. 1 ,

TIlE EFFECfS OF CAMELS ON FORAGE FOR MOUNTAIN GAZELLES AND NUBIAN IBEX IN SAUDI ARABIA

A TIlESIS SUBMITIED TO mE FACULTY OF TIlE GRADUATE SCHOOL OF mE UNIVERSITY OF MINNESOTA BY

JOHN PATRICK CAMPBELL

IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE

JUNE 1996

• ABSTRACf

Recent changes in the management of livestock in Saudi Arabia have led to changes in

the ecology of Arabia's rangelands. This study focuses on the effects of camels on the

availability of forage for mountain gazelle (Gazella gazella) and Nubian ibex (Capra ibex

nubiana) in central Saudi Arabia. I investigated the growing season food choices of

gazelle and ibex, how camels affect the availability of those important forage species and

the effects of camels on the their primary dry season forage, Acacia tortilis. The study

relies on comparisons made between an area with camels and an area where fences

exclude camels. Gazelle and ibex can move freely between the 2 areas. Gazelle and ibex

were found to be primarily browsers. The most important species during the growing

season were small perennial shrubs. The density and canopy cover, and hence availability,

of most growing season species important to gazelle and ibex were greater in the area of

camel exclusion. During the dry season, Acacia tortiUs is the primary forage species for

gazelle and ibex. Camel browsing creates a canopy shape that produces more available

forage, foliage and twigs. However owing to a greater abundance of A. tortilis trees in

the forage producing size class, there is more forage available in the camel exclusion zone.

- 1 TABLE OF CONIENTS

ABSTRACT .... i

TABLE OF CONIENTS ii

LIST OF TABLES . . v

LIST OF FIGURES . ix

ACKNOWLEDGMENTS. x

INTRODUCTION . . . 1

I. FOOD HABITS OF MOUNTAIN GAZELLES AND NUBIAN IBEX DURING THE GROWING SEASON IN SAUDI ARABIA 2

Abstract. . 2 Introduction 3 Study Area. 3 Methods. . 4 Results . . 5 Discussion . 6 Literature Cited 10 1 II. THE EFFECTS OF CAMELS ON MOUNTAIN GAZELLE AND NUBIAN IBEX FORAGE IN SAUDI ARABIA 16 " J

Abstract. . 16 Introduction 17 I Study Area. 21 Climate. 21 Vegetation . 22 1 Fauna 23 Livestock . 24 Methods. . . 24 Experimental setting. 24 Density of camels. . 25 Vegetation measures. 25 Density and percent cover ofperennial plants. 26 Above~ground biomass of principal forage plants 26 Community diversity...... 27 - 11 Table of contents (cont.) Page

Statistical analyses 27 Results . . . . . - . 28 "t: Density of camels. 28 [ I­ Vegetation. . . 28 f Species richness and di-:ersity . 28 Density...... 28 i\ Cover ...... 29 • Biomass of 3 principal gazelle and ibex foods. [, 30 t Discussion...... 30 r' r~ Effects of camels on forage availability for wild herbivores 31 t. Diversity ...... 31 I r:r Density and cover ...... 32 I,' Potential effects of camels on non-forage resources. 33 ~, f Protective cover ...... 33 f y- <;: • f OJ ucceSSIOn...... 34 ;, Conclusions and management recommendations. 35 ~" i'.' Literature Cited ...... 38 F III. TIIE EFFECTS OF CAMELS ON THE A V AILABILITY OF ACACIA TORT/US FORAGE IN THE IBEX RESERVE, SAUDI ARABIA. 57

Abstract. . 57 Introduction 59 Study Area. 61 Methods. . 62 Sampling design 62 Density. . . 63 Canopy dimensions 64 Availability of foliage 64 Estimated removals by browsing. 65 Regressions. 66 i Results . . . . 66 Density. . . 67 l Height classes . 67 Canopy dimensions :1 67 ;1 Availability of forage 68 q Estimated removals by browsing. 68 ,\1 'j Twig length 69 i,i ;;J Regressions. 69 "'i Discussion. . 69 - iii Table of contents (cant.)

Literature Cited ...... 74

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IV l

I~ LIST OF TABLES I. GROWING SEASON FOOD HABITS

Table 1. Perennial plant species eaten by mountain gazelle and Nubian ibex during the growing season in The Ibex Reserve, I Saudi Arabia, 1994...... 14 I II. EFFECTS OF CAMELS ON FORAGE Table 1. Seasonal density ofcamels in Wadi Matham, The Ibex I Reserve, Saudi Arabia. 1994...... 42 Table 2. Results of Shannon-Weaver diversity tests conducted in the alluvial fan vegetation type, Wadi Matham, The Ibex I Reserve, Saudi Arabia, 1994...... 42

Table 3. Results of Shannon-Weaver diversity tests conducted I in the island vegetation type, Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994...... 42

I Table 4a. Mean density (individuals/ha) of perennial grass species in the alluvial fan vegetation type, Wadi Matham, The I Ibex Reserve, Saudi Arabia, 1994...... 43 Table 4b. Mean density (individuals/ha) of perennial dwarf shrub I and vine species in the alluvial fan vegetation type, Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994. . " .... 44 t Table 4c. Mean density (individuals/ha) of perennial forb species in the alluvial fan vegetation type, Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994...... 45

Table 4d. Mean density (individuals/ha) of perennial shrub and tree species in the alluvial fan vegetation type, Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994...... 45

Table 4e. Perennial plant species recorded in the alluvial fan vegetation type, Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994, for which mean density was estimated at less than 100 individuals/ha in both treatment types ...... 46

- v List of tables (eont.)

Table 5a. Mean density (individualslba) ofperennial grass species in the island vegetation type, Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994...... 47

Table 5b. Mean density (individualslba) of perennial ~~varf shrub species in the island vegetation type, Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994...... ' ...... 48

Table 5c. Mean density (individualslha) of perennial forb species in the island vegetation type, Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994...... 48

Table 5d. Mean density (individual sib a) of perennial shrub species in the island vegetation type, Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994...... 49

Table 5e. Perennial plant species recorded in the island vegetation type, Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994, for which mean density was estimated at less than 100 individualslha in both treatment types...... 49

Table 6. Mean total percent canopy cover for all perennial plant species combined in 2 vegetation types, Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994...... 50

Table 7a. Mean canopy cover of perennial grass species in the alluvial fan vegetation type, Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994...... 50

Table 7 b. Mean canopy cover of perennial dwarf shrub species in the alluvial fan vegetation type, Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994...... 51

Table 7c. Mean canopy cover of perennial forb species in the alluvial fan vegetation type, Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994...... 51

Table 7d. Mean canopy cover of perennial tree and shrub species in the alluvial fan vegetation type, Wadi Matham, The Ibex - Reserve, Saudi Arabia, 1994...... 52 Vl List of tables (cont.)

Table 7e. Perennial plant species recorded in the alluvial fan vegetation type, Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994. for which mean canopy cover was estimated at less than 0.1 % in both treatment types...... 52

Table Sa. Mean canopy cover of perennial grass species in the island vegetation type, Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994...... 53

Table 8b. Mean canopy cover of perennial dwarf shrub species in the island community type, Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994...... 53

Table 8e. Mean canopy cover of perennial tree and shrub species in the island community type, Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994...... 54

Table 8d. Perennial plant species recorded in the island vegetation type, Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994, for which mean canopy cover was estimated at less than 0.1 % in both treatment types...... 55

Table 9. Above-ground biomass (kg/ha) of 4 perennial plant species important as forage for mountain gazelles and Nubian ibex in the alluvial fan vegetation type, Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994...... , .... 56

Table 10. Above-ground biomass (kgfha) of 3 perennial plant species important as forage for mountain gazelles and Nubian ibex in the island vegetation type, Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994...... 56

IlL EFFECrS OF CAMELS ON TIIE A V AILABILITY OF ACACIA TORT/LIS FORAGE

Table 1. Relative abundance classifications for 3 herbivores in 4 sites in The Ibex Reserve, Saudi Arabia, 1994...... 77

Table 2. Mean density (individuals/ha) ofAcacia tortilis by height class among 4 sites in Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994...... 77

vii List of tables (cont.)

Table 3. Mean height (m) of Acacia tortilis trees> 0.25 m height among 4 sites, Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994...... 77

2 Table 4. Mean canopy area (m ) of Acacia tortilis trees> 0.25 m height among 4 sites, Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994...... 78

Table 5. Mean available Acacia tortilis foliage (kg/l:ta) from 2 height classes in a protected and unprotected site, The Ibex Reserve, Saudi Arabia, 1994...... 78

Table 6. Number and proportion of Acacia tortilis trees with actively growing twigs among 4 sites in Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994...... 79

Table 7. Mean number of twigs per Acacia tortilis tree in a site protected from camel browsing and a site unprotected from camel browsing. Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994.. . . . 79

Table 8. Mean length (cm) of actively growing Acacia tortilis twigs in a site protected from camel browsing and a site unprotected from camel browsing. Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994...... 79

Table 9. Comparison ofleast squares lines among 4 sites, Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994...... 80

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I LIST OF FIGURES I I. GROWING SEASON FOOD HABITS Figure 1. Location ofThe Ibex Reserve, Saudi Arabia . . 12 I Figure 2. Study area in the Wadi Matham watershed, The Ibex Reserve, Saudi Arabia ...... ' ...... 13

I III. EFFECTS OF CAMELS ON THE AVAILABILITY OF ACACIA TORTIUS FORAGE

I Figure 3. Proponions of height classes ofAcacia tortilis among 4 sites, Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994...... 80 I I I I I I I I I­ I ~ I IX I ACKNOWLEDGMENTS

I could not have completed this project without guidance and support from many

people. I apologize for anyone I neglect to mention.

I would like to thank His Royal Highness Prince Saud al Faisal, managing director of

the Saudi Arabian National Commission for Wildlife Conservation and Development

(NCWCD), for his support of conservation in the kingdom. I am indebted to Dr.

Abdulaziz Abuzinada, secretary general of the NCWCD, for his support of this project and

the people of Saudi Arabia for making me feel welcome in their country.

I am grateful to Alexandra Dixon, director of conservation and consultancy, The

Zoological Society of London, for allowing me the opportunity to conduct this project as

part of my employment responsibility and especially for her patience.

My colleagues in Saudi Arabia at the King Khalid Wildlife Research Centre (KKWRC)

provided endless guidance and encouragement. I would like to thank Fay Robertson for

her patience and enthusiasm while teaching me the flora of Saudi Arabia and her

wonderful ability to identify the remains of individuals that had been ravaged by insatiable

camels. Without Fay this project would not have been possible. I thank Kevin Dunham

and Tim Wacher for helping with the study design. Jacques Flamand who believed that

something positive would come out of this, Mr. Fadl for endless administrative support

and good cheer, Nigel Brown for encouragement and Charlie Kitchenside for that much

needed kick in the ass. I also thank all of them for making me feel at home when I was - half a world away. x I am grateful to my graduate committee members Ken Brooks and Tony Starfield for

critical reviews of the manuscript and to my principal advisor Peter Jordan for giving me a

chance when no one else would. I also thank Frank Martin for his statistical advice.

A sincere thanks to all my friends in Minnesota for their support and more importantly,

the much needed distractions they provided. A special thanks to Rob Iensen and Mary

D~rr for their ceaseless letters while I was away. Thanks for not forgetting me.

And most of all, I thank my parents, John and Patricia Campbell, who never quite

understood why I do what I do, but never "seriously" questioned and always supported it

anyway.

xi

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This thesis is arranged into 3 chapters, each containing results and discussion that stand

alone. The study areas, although in the same region for all 3 chapters, are often subtly

different and therefore have been re1escribed in each chapter. The flrst chapter examines

the growing season food choices of mountain gazelle and Nubian ibex in The Ibex

Reserve, Saudi Arabia. The second chapter builds upon the flrst by examining the effects

of camels on plant species found to be important for gazelle and ibex. The third chapter

examines the effects of camels on the availability ofAcacia tortilis, the primary forage for

gazelle and ibex during the dry season. Chapters 2 and 3 discuss historical aspects of

camel grazing in Saudi Arabia and possible explanations for observed differences in

availability of forage.

- I: \\ il r I i Food Habits of Mountain Gazelle and Nubian Ibex During the Growing Season in Saudi Arabia

Abstract: I examined perennial plants eaten by mountain gazelle (Gazella gazella) and

Nubian ibex (Capra ibex nubialUl) during the 1994 growing season in the Ibex Reserve, central Saudi Arabia. I established transects to systematically locate plants which were then given a numeric browse rating. Both gazelle and ibex were found to be primarily browsers during the growing season. Of the 48 perennial plants examined, 80% were browse species (woody plants) and only 9% were not eaten.

Key Words: Capra ibex nubiana, food habits, Gazella gazella, mountain gazelle, Nubian ibex, Saudi Arabia

2 I, INTRODUCTION The mountain gazelle (Gazella gazella) and Nubian ibex (Capra ibex nubiana) are 2 ~ species of special concern in Saudi Arabia. Populations of both have been reduced in

numbers and distribution throughout Arabia during the past century. Until recently there ~ have been few ecological studies on either species in Arabia and these have focused on , their status and distribution (Green 1984, Green 1986, Habibi 1986, Flarnand et al. 1988, , Habibi and Grainger 1990, Thouless et al. 1991, AI-Hazmi and Ghandour 1992). Thus, there exists little information on the food habits of these animals within the Arabian .a peninsula. I determined the use of perennial plants by gazelle and ibex as part of a larger , study in The Ibex Reserve. , STUDY AREA , The Ibex Reserve is located in central Saudi Arabia 150 km southwest of Riyadh at 23° 30'

2 N. and 46° 30' E. (Fig. 1). The reserve, some 2,000 km , has a surface area of ca. 75% ~ undulating plateau and 25% wadis (Robertson 1993). Wadis are relatively low lying areas that .­ collect precipitation run-off from surrounding upland areas. The wadis have eroded into the

upper plateau creating deep canyons with steep sided walls 100 - 300 m high, and the floor is .I typically 200 - 500 m wide. The study area was in Wadi Ghaba, which is part of the Wadi .I Matharn watershed (Fig. 2). .­ The reserve is considered a hyper-arid desert with clearly defined cool and warm

seasons and rainfall is restricted almost exclusively to the cool months, October to April J • (Mandaville 1990). Mean annual rainfall in the reserve has been estimated to be 50 mm J 3 J I I (Habibi and Grainger 1990). Summer months, May to August, are intensely hot with a daily maxima ca. 45-50°C. Winter maxima are ca. 22°C and minima average 10°C,

I occasionally dropping below O°c. (Child & Grainger 1990). Dunham (unpubl. data) I reports the mean relative humidity near Riyadh in August 1995 was 10%. I Mandaville (1990) classifies The Ibex Reserve as being within the Sudanian Plant- Geographic Region. Vegetation in the reserve is found almost exclusively in the wadis.

I Two indigenous ungulates exist in the study area: mountain gazelle, and Nubian ibex. I METHODS

I Perennial plants were sampled during the growing season, May and June 1994. A rapid, I semi-quantitative, rank estimate of plant use, based on visual browse impact, was used to determine an index of food choices for gazelle and ibex. Due to time constraints, it was

I impractical to determine the individual choices of the 2 herbivores. Therefore, data for gazelle I and ibex were combined. I In 1990, a fence was placed across Wadi Ghaba. This fence excluded camels from a section of the wadi, but allowed free movement of gazelle and ibex. I conducted the study entirely I within the camel exclusion zone of Wadi Ghaba; therefore, all evidence of browsing was known I to be by gazelle or ibex. Transects were established in 3 plant communities. The communities were chosen because they represent the habitats that gazelle and ibex were observed to frequent

I regularly. Transects were based on a random starting point and ran east-west to run parallel to

the long axis of the sampling unit. Transect width was defined as the distance to which I could - I visually identify plant species and it extended the length of the vegetation type. Each perennial ..I 4 I I plant species was given a browse rating based on extent of removal of current growth. A value

of zero (0) corresponded to no removal of plant tissue. A value of '3' corresponded to

extensive removal of plant tissue. Values of '1' and '2' were intermediate. An attempt was

made to coUect data from 30 individuals of each species. Once 30 individuals were assessed, no

more data were collected for that species.

The mode, or most common browse rating for a species, was used as an index of forage use

for that species. High mode values suggested that a plant species was a common component of

gazelle and ibex diets and was an important forage species. As an additional measure, the

frequency of non-zero values for a species was calculated. High frequencies suggested that

gazelle and ibex were actively seeking that species while a low frequency would suggest that it

was eaten only when encountered. The mode values were then placed into arbitrarily chosen

use groups. Mode values of zero in combination with a frequency rating of zero were

considered not eaten by gazelle or ibex; mode values of zero with a frequency rating greater

than zero were considered low-use; mode values of 1 were considered medium-use; and mode

values of 2 and 3 were considered high-use.

RESULTS

Gazelle and ibex in The Ibex Reserve had a diverse diet. A total of 48 perennial plant

species were examined (Table 1). Of the 44 species with adequate sample sizes (n >= 10),

8 (18%) were found to be high-use (mode =2 or 3) and 12 (27%) were medium-use

(mode =1). Only 4 (9%) showed no evidence of use (mode and frequency =0). Sixteen

of the 20 (80%) medium and high-use species were browse species. Only 2 forbs,

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", ,~~ ~i~,' -"'"'" ' j " .,. ~ .~,,~" , , Farsetia spp., and Aervajavanica and 2 grasses, Stipagrostis spp., and Hyparrhenia hirta , were considered to be in the medium or high-use categories.

, DISCUSSION I This study focused exclusively on the use of perennial plant species. Owing to below­ average rainfall during 1994 (18 mm), annual forbs and grasses were rare and therefore I not an available food source. It is not known whether gazelle or ibex would have fed I upon annuals if they were available. The study was conducted at the height of the growing season when herbivores were provided with the widest annual variety of foods.

~ Like most herbivores, gazelle and ibex probably vary their diets seasonally. Gazelle and

ibex were observed to feed almost exclusively on Acacia torti/is in the autumn or dry - season. During the dry season, A. tortilis and A. ehrenbergiana typically remain green ~ and actively growing; therefore, gazelle and ibex most likely tum almost exclusively to I browse during the dry season. Gazelle and ibex in Saudi Arabia were primarily browsers. Flamand et al. (1988)

I observed that browse formed a substantial portion of the diet of Farasan gazelle (Gazella I gazella) on the Farasan Islands. AI-Hazmi et al. (1992) also found Farasan gazelle to be I browsers; although, mountain gazelle on the mainland had a more varied diet of grasses, forbs and browse. Habibi (1994) has shown that ibex in Saudi Arabia have a mixed diet

I He states that they feed primarily on A. toreWs trees, forbs and grass, depending on _I availability. Habibi's (1994) list of plants eaten by ibex is similar to results of this study. ..­ Many other arid land gazelle species such as dorcas gazelle (Gazella dorcas), sand gazelle 6 I I (Gazella subgutturosa marica), Indian gazelle (Gazella gazella), Chinkara (Gazella

bennetti) and dama gazelle (Gazella dama) are also primarily browsers (Carlisle et al.

1968, Berwick 1974, Shama 1977, Essghaier 1981, Baharav 1982, Ghosh 1986,

Grettenberger 1986, Grettenberger 1987, Mohamed et al. 1991). Contrary to these

findings. both mountain gazelle and dorcas gazelle were primarily grazers during the

growing season in Israel (Baharav 1980, 1981, 1983); although. the importance of browse

increased after the growing season. Furthermore. 2 of the Israeli sites had much greater

annual precipitation than the Arabian site. This may have produced a wider range of plant

species to choose from.

Both gazelle and ibex were tolerant of several plant species exhibiting chemical

defenses. Most interesting was that both gazelle and ibex fed upon the large, rubbery,

evergreen leaves of Calotropis procera. Leaves of C. procera are filled with a latex-like

fluid that contains calotropin, a toxin that has been used by indigenous peoples to make

poison arrows (Mandaville 1990). C. procera was avoided by domestic livestock and was

one of the only species entirely avoided by camels in the region. However, Bedouin have

been known to force-feed camels C. procera as an antihelminth and to cure nightblindness

which may be a result of vitamin A deficiency (Abbas et al. 1992). Another species,

Haloxylon salicornicum, or saltbush, contains a high concentration of salt. This was

found to be in the medium-use category. It was also eaten by camels, especially during the

dry season. Mandaville (1990) states that ~xcessive browsing can be physiologically

damaging to livestock.

- 7 & , Cucumis prophetarum and Citrullus colocynthis were classified as low-use. However, , both gazelle and ibex have been observed to eat the bitter melons produced by these plants. The fruits are known to be toxic in large doses, and the pungent taste make them a. difficult to eat' Camels avoided both species. , Lavandula coronopifolia was found to be a heavy-use species. However, I observed little use of this species from early summer through late autumn. Gazelle and ibex may

, have been eating L. coronopifolia during late winter because little else was available. , Bites recorded may have been remnant from the end of the dry season. Another species, Poiycarpea repens was found to be a low-use species; however, this result may not be

I. accurate. F. Robertson (pers. comm.) believes that P. repens may actually be a heavy-use

species. P. repens is a small perennial forb of sandy soils and if a gazelle or ibex were to •a feed upon it, they could easily consume the entire plant, thus removing any evidence of its presence. I often observed gazelle feeding in open areas on obviously small plants. Upon I examination of the, area I found that P. repens was quite abundant. I Two grass species, Hyparrhenia hirta and Chrysopogon plumulosus, were extensively grazed in July. Both species were avoided in the spring when this study was conducted.

I Therefore, I would consider both to be at least used at a medium level if not high. I Another grass species, Cymbopogon commUlalus, was also extensively grazed in July. , However, this species was restricted to the edges of scree slopes and therefore browsing may have been by rock hyrax (Procavia capensis) as well as gazelle and ibex. , The Ibex Reserve is located in an extremely arid region and overall biomass of vegetation is relatively low. Furthennore, camels are abundant and widespread .', 8 ,

iIII _. •• ""', ' I

throughout Wadi Matham. Therefore, camels may be having significant impacts on the 1 availability of important gazelle and ibex forage species. Future studies should attempt to I determine specific needs of each of the herbivore species and overall availability of food 1 resources. This would better enable managers to develop management plans for The Ibex

Reserve. 1

1

- 9 .. ~ LITERATURE CITED Abbas, B., A. E. El Tayeb, and Y. R. Sulleiman. 1992. Calotropis procera: feed -. potential for arid zones. The veterinary record, August 8 1992. Al-Hazmi, M. A., and A. M. Ghandour. 1992. An ecological study of gazelle in the western and southern regions of Saudi Arabia. J. of Arid Environ. 23:279-286.

- Baharav, D. 1980. Habitat utilization of the dorcas gazelle in a desert saline area. J. of , Arid Environ. 3: 161-167.

Baharav, D. 1981. Food habits of the mountain gazelle in semi-arid habitats of eastern , Lower Galilee, Israel. J. of Arid Environ. 4:63-69.

Baharav, D. 1982. Desert habitat partitioning by the dorcas gazelle. J. of Arid Environ. I 5:323-335.

Baharav, D. 1983. Observation on the ecology of the mountain gazelle in the Upper I Galilee, Israel. Mammalia 47:59-69.

Berwick, S. H. 1974. The community of wild ruminants in the Gir Forest ecosystem, I India. Ph. D. Thesis, Yale Univ., Hartford.

Carlisle, D. B., and L. 1. Ghorbial. 1968. Food and water requirements of dorcas gazelle I in the Sudan. Mammalia 32(4):570-576: I Child, G. and J. Grainger. 1990. A System Plan for Protected Areas for Wildlife Conservation and Sustainable Rural Development in Saudi Arabia. pub. Saudi Arabian National Commission for Wildlife Conservation and Development & I IUCN. 335 pp. Essghaier, M. F. A. 1981. Ecology and behavior of dorcas gazelle. Ph. D. Thesis. Univ. I of Idaho, Moscow.

Flamand, J. R. B., C. R. Thouless, H. Tatwany, and J. F. Asmode. 1988. Status of the I gazelle of the Farasan Islands, Saudi Arabia. Mammalia 52(4):608-610.

Ghosh, P. K., S. P. Goyal and H. C. Bohra. 1986. Habitat utilization by wild and I domestic ungulates -- A case study in a desert biome. Pages 549-550 in P. J. Joss, P. W. Lynch and O. B. Williams, eds. Rangelands: A resource under siege: I proceedings of the 2nd Int. Rangelands Congress. Australian Acad. of Sci., - Canberra. ~ I 10 I I

Green, A. A. 1984. Wildlife reconnaissance surveys in AI-Jouf province. FAO field doc. I no. 1. FAO. Rome. Mimco. Green, A. 1986. Status of large mammals of northern Saudi Arabia. Mammalia 50: 483­ 493. I

Grettenberger, J. 1987. Ecology of the dorcas gazelle in northern Niger. Mammalia 51(4):527-536. I Grettenberger, J. F. and J. E. Newby. 1986. The status and ecology of the dama gazelle I in the Air and Tenere National Nature Reserve. Niger. BioI. Cons. 38:207-216.

Habibi. K. 1986. Arabian ungulates - their status and future protection. Oryx 20: 100­ I 103.

Habibi. K. 1994. The desert ibex. Immel Publishing. London. 192 pp. I

Habibi. K. and J. Grainger. 1990. Distribution and status of Nubian ibex in Saudi Arabia. Oryx 24(3):138-142. I

Mandaville, J. P. 1990. Flora of Eastern Saudi Arabia. Kegan Paul International, London. 482 pp. I

Mohamed. S. A.• J. Abbas and M. Saleh. 1991. Natural diet of the Arabian rheem gazelle. Gazella subgutturosa marica. J. of Arid Environ. 20:371-374. I

Robertson, F. 1993. Camel densities in the Special Ibex Reserve at Hawtah Bani Tamim. Report to the Saudi Arabian National Commission for Wildlife Conservation and I Development. 15 pp.

Shama,1. K. 1977. Ecological study of habitats, feeding and survival of the gazelle (Gazella gazella). J. of the Bombay Nat. Hist. Soc. 74(2):347-350.

Thouless. C. R., J. G. Grainger, M. Shobrak and K. Habibi. 1991. Conservation status of gazelle in Saudi Arabia. BioI. Cons. 58(1):85-98 .

.. 11

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Egypt Saudi Arabia

~ The Ibex Reserv

Rgure 1:. Location of The Ibex Reserve, Saudi Arabia

12 I I 5 'liliiiiii i ~ I !

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t~adl Ghaba

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Figure 2. Map of the Wadi Matham watershed, The Ibex Reserve, Saudi Arabia 1994

13 Table 1. Perennial plant species eaten by mountain gazelle and Nubian ibex during the growing season in Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994. Mode refers to an index of use: Mode values of zero in combination with a frequency rating of zero were considered not eaten by gazelle or ibex; mode values of zero with a frequency rating greater than zero were considered low-use; mode values of 1 were considered medium- use; and mode values of2 and 3 were considered high-use.

A. S~cies for which at least 10 individual Elants were examined are listed Species Physiognomt Family N Frequencyb Mode = 3 Calotropis procera S Asclepiadaceae 30 1.00 F arsetia spp. F Cruciferae 30 1.00 Hibiscus micranthus St Malvaceae 30 1.00 Rhynchosia memnonia V Leguminosae 30 1.00 Lavandula coronopifoUa St Labiatae 30 0.93

Mode =2 Ephedra foliata V Ephedraceae 25 1.00 Acacia ehrenbergiana S;T Leguminosae 30 0.97 Convolvulus glomeratus V Convol vulaceae 30 0.97

Mode = 1 Grewia spp. S Tiliaceae 10 0.90 Haloxylon salicornicum S Chenopodiaceae 30 0.90 Anvillea. garcinii St Compositae 30 0.87 Lycium shawii S Solanaceae 30 0.80 Stipagrostis spp. G Poaceae 30 0.80 Acacia torcilis S;T Leguminosae 30 0.70 Gymnocarpus decandrum St Caryophyllaceae 27 0.70 Helianthemum Jipii St Cistaceae 30 0.70 Abutilon fruticos um St Malvaceae 30 0.63 Salvia aegyptiaca St Labiatae 30 0.63 Hyparrhenia hirta G Poaceae 30 0.60 Aerva javanica F Amaranthaceae 30 0.53 Table 1. part A. (cont.)

Species Physiognomy· Family N Frequencl Mode =0 H eliotropium ramosissimUm St Boraginaceae 30 0.53 Boerhavia elegans F Nyctaginaceae 30 0.43 Pulicaria undulata St Compositae 30 0.40 Polycarpea repens F Caryophyllaceae 27 0.37 Cenchrus ciliaris G Poaceae 30 0.33 Citrullus colocynthis F Cucurbitaceae 16 0.31 Tetrapogon villosus G Poaceae 25 0.24 Zilla spinosa St Cruciferae 30 0.20 F arsetia burtonae F Cruciferae 12 0.17 Sporobolus nervosus G Poaceae 30 0.17 Chrysopo gon plumulosus G Poaceae 30 0.13 Dichanthium Joveolatum G Poaceae 24 0.13 Pennisetum divisum G Poaceae 26 0.12 Tricholaena teneriffae G Poaceae 29 0.10 Chrozophora oblongifolia F Euphorbiaceae 11 0.09 Cynodon dactylon G Poaceae 26 0.08 Astragalus sieberi St Leguminosae 14 0.07 F agonia bruguieri St Zygophyllaceae 30 0.07 Pulicaria glutinosa St Compositae 30 0.07 Octhochloa compressa G Poaceae 16 0.06 Echinops sp. F Compositae 14 0.00 Lasiurus scindicus G Poaceae 14 0.00 OropetiumlTripogon c G Poaceae 14 0.00 Panicum turgidum G Poaceae 30 0.00

B. Species for which less than 10 individual plants were examined are listectd Species Physiognoml Family N Frequencyb Commicarpus spp. F Nyctaginaceae 1 1.00 CUCumlS prophetarum F Cucurbitaceae 8 0.50 Cymbopogon commutatus G Poaceae 6 0.67 Rhazya stricta S Apocynaceae 5 0.00 • G = grass; F = forb; S =shrub; St = dwarf shrub; T = Tree; V =vine b The frequency of non-zero values in the sample.

C The following three species: Oropelium capense, Tripogon africanus, T. multiflorus could not be reliably differentiated in the field. d Modes not presented because sample sizes are too small. - 15

pi The Effects of Camels on Mountain Gazelle and Nubian Ibex Forage in Saudi Arabia

Abstract: Effects of camels on the availability of forage for mountain gazelle (Gazella

gazella) and Nubian ibex (Capra ibex nubiana) were measured during the 1994 growing

season in Saudi Arabia. The study relies on comparisons made between an area with

camels and an area where fences exclude camels. Gazelle and ibex can move freely

between the 2 areas. Density and canopy cover of perennial plant species were compared

between 2 plant communities. The results were then related to plant species that were

important forage species for gazelle and ibex. Plant species with a higher density and

canopy cover in the camel exclusion zone tended to be important forage species while

species with a higher density and canopy cover in the camel grazing zone tended not to be

important forage species. Total canopy cover was greater in both vegetation types after

protection from camels. Above-ground biomass was measured for several important

forage species. Total above-ground biomass and edible biomass tended to be greater in

the camel exclusion zone. The results suggest that camels are having a negative impact on

the availability of forage for gazelle and ibex.

Key Ward..;;: Capra ibex nubiana, dromedary camel, forage, Gazella gazella, livestock .. impacts, mountain gazelle, Nubian Ibex, Saudi Arabia - ..

.... 16 INTRODUCTION

It is generally accepted that domestication of ungulates was well established in

Southwest Asia by 10,000 years BP (Ryder 1984, Clutton-Brock 1987). This practice

spread rapidly throughout the vast arid lands that currently extend from North and East

Africa to western India. On the Arabian peninsula, there is evidence of nomadic herders

grazing cattle and sheep in the southwest. along the Red Sea coast, 7,000 years BP (Child

and Grainger 1990). Rapid climate changes beginning 4,000 years BP caused further

desiccation of Arabia and led to the replacement of cattle with sheep and goats (Child and

Grainger 1990). Climate changes also limited herders' abilities to graze their livestock in

the more arid interior. Possibly as a result, the camel, because of its arid-land adaptations,

was domesticated, this taking place in the southern half of Saudi Arabia between 4,500

and 5,000 years BP (Zeuner 1963, Epstein 1971, Ripinsky 1975, Gauthier-Pilters and

Dagg 1981, Bulliet 1990). Domestic camels allowed herders to penetrate further into the

arid interior of Arabia and to remain there longer, because of their generalist diet and

ability to tolerate water scarcity. Domestic camels spread rapidly through the Middle

East. Midianite herders from Arabia had reached Jordan with their camels by 3,000 years

BP and Arabia was well established as a camel breeding country by 670 BC when Arabian

kings began supplying camels for military purposes (Ripinsky 1975). However, this was

not new territory for camels. The earliest documented case of the camel in Arabia is a

probable wild camel from southwest Saudi Arabia estimated at nearly 9,000 years BP

(Grigson et al. 1989). Further fossil evidence suggests that wild camels were present in

Arabia by the Middle Pleistocene (Zeuner 1963, Ripinsky 1975, Zarins 1978). 1berefore,

- 17 I I camels and other wild ungulates had probably been co-existing in Arabia for thousands of years before domestication. Despite the probable existence of wild camels in Arabia, the

I arrival of domestic camels, along with sheep and goats. would inevitably alter the I character of the arid-land vegetation in Saudi Arabia, an event that would be repeated many times over as domestic livestock spread throughout the arid lands of Asia and

I Africa. Child and Grainger (1990) believe that the ecology of the Arabian ranges has been I changing for thousands of years due to livestock. However, these changes have been I gradual and presumably did not lead to large modifications in the distribution and abundance of indigenous ungulates (Child and Grainger 1990). While patterns of forage

I competition between wild and domestic ungulates cannot be reconstructed, those wild I ungulates still present in 1900 offer an estimate of what species, by region, had adapted, over the millennia, to livestock presence. I I Recent historic. cultural and political background: Historically, the impact of livestock on the rangelands of Saudi Arabia was constrained

I by the availability of free water and forage. The nomadic herders moved only on foot, and I access to ranges was traditionally allocated by a tribally-based system of "hemas" or I grazing rights (Batanouny 1986, Green 1986, Habibi 1986, AI-Sharif 1990, Sulayem and Joubert 1994). With the sudden great wealth from oil in the 1940s, the Saudi government

I started providing herders with water delivered by truck, subsidized fodder and subsidized . I vehicles for transporting stock (Child and Grainger 1990, Thouless et al. 1991, Dunham et - al. 1993). At the same time, much of the country was declared public domain, eliminating ..I 18 I I the tribal allocations or hemas. All this led to increased domestic herd sizes, entry into

remote regions previously not accessible, immigration by outsiders into prime rangelands

and a loss ofthe nomadic life style (Child and Grainger .1990). Local, year-round grazing

became common. These relatively rapid changes in livestock numbers and management

led to a rapid decline in the grazing resources over the last 30 to 40 years (Allred 1968,

Child and Grainger 1990) and they may have impacted whatever wild ungulates were

present, eliminating previous refugia unavailable to longterm use by livestock.

During the same decades, wild populations of herbivores in Saudi Arabia also

underwent striking changes. Until early in the 19008,5 ungulates were common on the

Arabian peninsula: mountain gazelle (Gazella gazella, with several subspecies), sand or

goitered gazelle (Gazella subgutturosa marica), Saudi dorcas gazelle (Gazella saudiya),

Arabian. oryx (Oryx /eucoryx) and Nubian ibex (Capra ibex nubiana) (Philby 1923,

Raswan 1935, Habibi 1986, vine Carruthers 1935). By the 1950s, the oryx and Saudi

dorcas gazelle had been extirpated and the other species were reduced to small, isolated

populations. Primary causes for these abrupt changes were habitat loss and unregulated

hunting with modern weapons and all-terrain vehicles (Raswan 1935, Child and Grainger

1990, Habibi 1994).

A national reaction to the loss of wildlife led to sharp policy shifts. In 1986, Saudi

Arabia established the National Commission for Wildlife Conservation and Development

(NCWCD) to establish reserves and protect natural biota. There are now 11 areas that

prohibit hunting and restrict livestock grazing (Sulayem and loubert 1994). Wildlife

breeding facilities, The King Khalid Wildlife Research Centre (KKWRC) and The National

- 19

-- ~ .

, ~

',,~__~" .. ~,~_c.;,w>" ' _ ",__ "" I I Wildlife Research Centre, were established for endangered ungulates from which mountain gazelles, sand gazelles and oryx have been successfully restored to parts of their former

I range. I Although illegal hunting has been greatly reduced, it is believed that habitat degradation I is still contributing to wildlife decline. Despite successful restorations and local increases in sand gazelles and ibex, the future of Saudi Arabia's large mammals is not secure as long

I as range resources are subject to over-use by livestock. For sustainable co-existence of I wild ungulates with livestock, as in previous centuries, research on range relations, including cooperative arrangements with herders. is needed.

I For arid lands of the Old World, there is far less understanding of the competitive I impacts of livestock upon original vegetation and original fauna than for arid regions of North America. Furthermore, in North America livestock presence is so recent that

I reconstruction of prior plant and animal communities is quite feasible compared to doing I so for the Old World. I This study, conducted in The Ibex Reserve, relates to recent changes in both wildlife and livestock within Saudi Arabia. I examined camel impacts on potential forage used by

I mountain gazelles and Nubian ibex. Camels are generalist herbivores that avoid few plant I: species. Gazelles and ibex, in the study area, are primarily browsers, feeding on small perennial shrubs and Acacia spp. (Chapter 1, Habibi 1994). I took the opportunity to

I' compare vegetation that was potential forage for the 2 wild species between an area with I camels, an unprotected site, and one without camels, a protected site. While not a replicated study. to be quantitatively extrapolated to the region, results can reveal striking ~ I: 20 Ii dynamic processes that lead to new insights for conservation in. this poorly understood

ecosystem.

STUDY AREA

The Ibex Reserve is located in central Saudi Arabia 150 km southwest of Riyadh at 23°

2 30' N., 46° 30' E. (see Chapter 1, Fig. 1). The reserve, some 2,000 km , has a surface area

of ca. 75% undulating plateau and 25% wadis (Robertson 1993). Wadis are relatively

low-lying areas that collect precipitation run-off from surrounding upland areas. The

wadis have eroded into the upper plateau creating deep canyons with steep-sided walls

100-300 m high. The floor of the wadis is typically 200-500 m wide, eventually opening

to several km near the mouth, 5 km below the study site. The study area was in the Wadi

Matham watershed, including Wadi Ghaba (see Chapter 1, Fig. 2).

Climate

Most of Saudi Arabia is considered hyper-arid desert with clearly defined cool and

warm seasons and rainfall restricted almost exclusively to the cool months, October to

April (Mandaville 1990). Precipitation in the reserve is highly variable both spatially and

temporally. Mean annual rainfall is estimated to be 50 mm (Habibi and Grainger 1990).

For Wadi Ghaba, it was 115.5 mm in 1991-92,99.0 mm in 1992-93 and only 18 mm in

1993-94 (Dunham unpubl. data).

Summer months, May through August, are hot with a daily maxima ca. 45-50° C. - Winter maxima are ca. 22° C and minima average 10° C., occasionally dropping below 0° 21 I I C. (Child & Grainger 1990). Relative humidity in summer is low: Dunham (unpubl. data) I reports that the mean near Riyadh during August 1995 was 10%.

I Vegetation I Much of central Arabia. including the Ibex Reserve. is classified as within the Sudanian Plant-Geographic Region (Mandaville 1990). Soils of the upper plateaus and scree slopes

I have a low penneability and so support negligible vegetation. Most run-off flows into I wadis, where it accumulates in irregular patterns corresponding to sharp variations in relief and soil type. Consequently, vegetation in the wadis is patchy, but for this study is

I classified into 3 types, according to Robertson (1995). The "alluvial fan" type occurs I where water, flowing down the walls of the canyon, spreads out locally over the floor of the wadi. Here, the small tree, Acacia tortilis, dominates and overall richness of plant

I species is higher than elsewhere. The "island" type occurs along margins of the main I channel of the wadi where occasional high-water overflows onto a floodplain-like strip I some 10-40 m wide. Here, acacia trees are sparse. the dominant vegetation being small shrubs and perennial grasses. Elsewhere, perennials are sparse and growth is typically

I annual forbs and grasses (Robertson 1995). I All plants measured in this study were perennials. During 1993-94, because total rainfall was only 18 mm, essentially no annuals appeared. I

- I ..I' 22 I I Fauna

There are 2 wild ungulates in the reserve: mountain gazelle and Nubian ibex. Mountain

gazelles were extirpated from the reserve in the early 1970s due to overhunting (Dunham

et al. 1993). Captive rearing of gazelles began in 1980; although KKWRC did not assume

management until 1987 and reintroductions of mountain gazelles were started in 1990. By

the end of 1994, following the release of 71 gazelles, the population had grown to 165

(Dunham pers. comm.). Gazelle density was estimated by Dunham (pers. comm.) as

15.3{km2 in the protected zone and 4.9!km2 in the unprotected zone.

Ibex survived locally despite the period of uncontrolled hunting probably through their

habit of using rugged cliffs as refugia. Habibi (1991,1992, 1993) estimated 250 ibex

within the reserve during the early 1990s, with distribution limited to the central portions

of the reserve, including the Wadi Matham watershed. Habibi (1994), describes Wadi

Ghaba (protected) as having a relatively high presence of ibex compared to Wadi Matham

(unprotected). - Gazelles are restricted to the wadi beds and adjacent scree slopes, while ibex are not

restricted in their movements; however, both species forage primarily in the wadi beds.

The only other common mammalian herbivore is the rock hyrax (Procavia capensis)

which remains on the scree slopes. The local rodent fauna has not been studied, but few

were observed during the study period.

- 23 Livestock

Only camels have been traditionally grazed in the Wadi Matham watershed (Dunham et

al1993). Camels have probably existed in the region of the reserve for several millennia.

Phllby (1922) mentions camels, as well as sheep and goats, as common in the region

during hls 1918 explorations.

METHODS

Experimental Setting

In 1990, camel-proof fences were erected across the entrances to wadis Ghaba and

Ghafar (see Chapter 1, Fig. 2) leaving those wadis camel-free for 4 years prior to this

study. Prior to fencing, plant communities in wadis Matham and Ghaba were relatively

similar (F. Robertson pers. comm.) and so these two were chosen for this comparative

study. By 1994, differences between the protected and unprotected zones were apparent, ~ presumably due to removal of camels from one side. All data, except camel surveys, were collected after the end of the wet season, May through July, 1994. ~. Plant measures, to be related to foraging, were confIned to the 2 plant communities that contained most of the potential forage: the alluvial fan and island types. During the study,

- I observed all 3 ungulates foraging primarily in these communities These communities - also contained the great majority of the plant species and biomass within the wadis. It was I reasoned that, if ecologically significant competition does occur between the wild I ungulates and the domestic one, these communities would be the focus of such interaction. J, I 24 I J

Density of Camels J

2 Density of camels was estimated within a 6.6 km sample area completely within Wadi ~ Matham. Camels were counted from a vehicle driven along the 12 km of road transecting

the sample area. From this road, width of the wadi could be viewed. The entire floor of J

lhe main wadi was considered to be the survey area; scree slopes and side canyons were J not surveyed. Camels rarely venture onto scree slopes and camel numbers in side canyons I were negligible during the daily sampling period, shortly after dawn when camels were most active. Mean density was determined from 16 surveys during summer, May through I July, and from 8 in autumn, October and November. ~

Vegetation Measures I Density, canopy cover and species-diversity of all perennial plant species and the I above-ground biomass for several species known to be imponant forage sources of

gazelles and ibex were estimated. I A 2 stage cluster design was used in sampling each treatment, protected and I unprotected (Cochran 1977). The landscape of wadi bottoms was stratified into 3 types:

alluvial fan, island and other; and only the first two were sampled. In each treatment area I (side of fence), 6 representative patches of each of the 2 types were selected at random. I These patches varied from ca. 0.5 - 3 ha., the alluvial fan patches being roughly triangular I and the island patches elongate. Within each of these, 10 random points were selected, each being the center of 2 nested plots, one of 2 and one of 4 m radius or 12.56 and I 50.26 m2 respectively. ,I - 25 I I I I I Density and Percent Cover of Perennial Plants: Using the smaller plot for shrubs, grasses and forbs and the larger for trees, Acacia

I spp., all plants with>1/2 their rooted stem inside were counted. Density of each species I at each plot was calculated and averaged to provide a patch density, and these in turn were averaged for an estimate of species' density within that treatment type.

I Canopy cover of plant species was sampled at each point by measuring intercept (cm) I along 5 m transects in the cardinal directions from each sample point and these measurements were translated into percent cover, by species, for the plot. The 10 cover

I" estimates for species were then used to calculate a mean for each patch, and these in tum I were averaged to estimate mean species' cover within that treatment type.

I Above-Ground Biomass of Principal Forage Plants: I Of species commonly used by camels and wild ungulates, several had shapes that led to I a poor relationship between available forage and density or cover. Consequently, for 4 of these, Stipagrostis spp.(grass), Hibiscus micranthus (small shrub), Convolvulus

I' glomeratus and Rhynchosia memnonia (vines), above-ground biomass was sampled. I; Biomass for Acacia tortilis is reported elsewhere (see Chapter 3). All above-ground material of the 4 species was collected from the 2 m radius plots. Samples were then air

I dried for 2 months and weighed (to the nearest 0.1 g) for total and for edible portions. I Estimated biomass of each species in each treatment type was derived as above for density ..­ and cover . Ii 26 If --.I iii

Community Diversity: [Ii Diversity of plant species was calculated according to the Shannon-Weaver index W (Shannon and Weaver 1949). To avoid problems of mixing groups oflow-density large

plants with high-density small ones, plant groups were analyzed separately: a) grasses; b) W forbs; c) dwarf shrubs (including vines); and d) large shrubs and trees. Indices were based W on plant densities. W

Statistical Analyses W The data were assumed to be nonnally distributed because of the large sample sizes Cn ~ =60). The primary units (patches, n =6) from the 4 populations were assumed to be chosen from an infmite number of possible primary units (N =infinity). And the subunits U (points, m =10) were assumed to be chosen from an infmite number of possible sub-units ~ (M =infinity). Means and variances were then calculated for each population based on

fonnulas described in Cochran (1977; pg. 278, eq. 10.16 and pg. 279, eq. 10.23). The U means and variances were then used to look for differences between treatments using ~ independent, Student's t-tests based on a 2-stage cluster analyses with units of equal size

assuming population variances not equal and degrees of freedom equal to n-l (Snedecor U and Cochran 1967, pg. 115). ~ ~ ~ U - 27 iJ ,

, RESULTS , Density of Camels Density of camels in Wadi Matham was high in both summer and autumn (Table 1), but

, density was higher during summer (P =0.01). These estimates of density are similar to -. those of Robertson (1993) and Dunham (1992) for Wadi Matham.

, Vegetation , The large tufted grasses, Panicwn turgidwn and Pennisetwn diviswn, in the , unprotected zone had been grazed to a height of several centimeters by camels. Therefore, they could not always be distinguished in the unprotected zone. However, II both could easily be distinguished from all other species. Both species are similar in shape, , size and habitat preference and neither is eaten by gazelles or ibex. Therefore, they were , combined as 1 group, "Penn./Pan.", for comparisons and statistical analyses. , Species Richness and Diversity Shannon-Weaver diversity indices were calculated for both vegetation types and

, classified by vegetative growth form (Tables 2 and 3). In both community types, richness I and diversity were similar for all growth forms.

I Density

Fifty-eight species of perennial plants were encountered during sampling for density in - - the alluvial fan community type and 53 species in the island community type. In the -'- 28 II .I

alluvial fan type, the density of 14 species was greater in the protected zone (10 species, P J <= 0.05; 4 species, P <= 0.10). The density of 8 species was greater in the unprotected .I zone (6 species, P <= 0.05; 2 species, P <= 0.10). A difference in density could not be

detected for 16 species and 19 species were rare (Tables 4a-e). In the island community, .I the density of 8 species was greater in the protected zone (6 species, P <= 0.05; 2 species, ~ P <= 0.10). The density of 10 species was greater in the unprotected zone (7 species, P .~ <= 0.05; 3 species, P <= 0.10). A difference in density could not be detected for 2 species and 32 species were rare (Tables 5a-e). ~ iii Cover Total canopy cover was greater in both vegetation types after protection from camels - (P < 0.001), (Table 6). Cover was nearly 5 times greater in the protected alluvial fan II community and 7 times greater in the protected island community.

Forty-nine species of perennial plants were encountered during sampling of canopy ~ cover in the alluvial fan community type and 44 species in the island community type ~ (Tables 7a-e and 8a-d). In the alluvial fan type, 25 species had a greater canopy cover in

the protected zone (P <= 0.05), a difference could not be detected for 4 species and 19 ~ species were rare. In the island community, 8 species had a greater canopy cover in the ~ protected zone (P <= 0.05), no species had a greater canopy cover in the unprotected

zone, a difference could not be detected for 2 species and 33 were rare. •I I II

- 29 ..I ~ Biomass of 3 Principal Gazelle and Ibex Foods

Biomass was detennined for 4 species in the alluvial fan community type (Table 9) and

3 species in the island community type (Table 10). In the alluvial fan community type, 2

species had greater total weight in the protected zone (P <= 0.01) and 3 species had

greater edible weight in the protected wne. In the island community type, 2 species had

greater total weight in the protected wne (P <= 0.05) and the same 2 species had greater

edible weight in the protected wne. Rhync/wsia memnonia, a vine, was the only species

in both community types that did not exhibit a greater edible biomass in the protected

zone.

Seed weight was also measured for Hibiscus micranthus. Seed weight in the alluvial

fan community type was greater in the protected zone (0.1 kg/ha in the protected wne vs.

0.002 kg/ha in the unprotected zone) (P <= 0.01), H. micranthus was not encountered in

the island community type.

DISCUSSION

Two measures often used to estimate availability of forage for wildlife are density and

percent canopy cover of plant species. Density, when measured over time, is valuable in

detennining population trends of forage species and for developing diversity indices, but it

provides little indication of biomass of a species. Although canopy cover provides little

indication of population trends, it can relate directly to the available biomass of forage.

Many researchers have used density and cover to describe effects of grazing (Gardner -! N

1950, Holechek and Stephenson 1983, Bock et al. 1984, Brady et al. 1989, Milchunas et W al. 1989, Skarpe 1990, Bock and Bock 1993). W For this study. no data were collected on density or canopy cover of plant species prior

to construction of the camel-proof fence. However, a series of photographs and W observations made by researchers (K Dunham and F. Robertson pers. comm.) shortly W after exclusion of camels suggest that there were no major cross-fence differences in

composition or structure of the plant communities. In addition, there are no obvious W environmental changes apparent across the fence. Therefore, differences in density and W I cover between the protected and unprotected zones are believed to be a direct result of

exclusion of camels. W The entire study was conducted within 1 wadi. Therefore, the data represent W differences in only 1 part of the reserve. Most wadis in the reserve are experiencing

similar or higher levels of use by domestic herbivores. Although plant community ~ composition and edaphic factors differ among wadis, we would expect similar impacts by ~ camels on the availability of forage elsewhere in the reserve. a.I

Effects of camels on forage availability for wild herbivores Ir.i Diversity ~ The most gross measure of camel effects on vegetation, diversity and richness of plant

species, showed little difference between protected and unprotected zones. Therefore, in . ~ this study the 2 measures provide little insight into the effects of camels on availability of IJ • forage. However, we must remember that the plant communities have been protected for W 31 t.I , , only 4 years. This may not be sufficient time to detect changes in richness and diversity. Furthennore, plant species intolerant of heavy grazing were probably eliminated many

I years ago. lit Density and cover

-. Camels are reducing the availability of gazelle and ibex forage in Wadi Matham. A

, majority of species showed no difference in density between the 2 sites and just as many , occur at higher densities in the protected zone as in the unprotected zone. However, of , the 14 species in the alluvial fan community and 8 species in the island community that had a higher density in the protected zone, 9 and 4 respectively were important forage species , (see Chapter 1) for wild herbivores. Further, of the 8 and 10 species having higher density in the unprotected zone, only 1 and 3 respectively are important forage species. This

II. suggests that camels are selecting the same plant species as gazelles and ibex and may be

reducing their abundance. Another issue we must consider is that camels have been •, heavily impacting the range for several decades. Many of the present plant species may have been declining in abundance for much of this time. Furthennore, many browse­ II intolerant species may have already been eliminated. However, due to a lack of historical , data, we may never know this. The effects of camels on canopy cover are even more striking, especially in the alluvial

fan community. Total vegetative cover in alluvial fan community is only 5.1 % with camels

• present Of this, over 70% of the cover is and both large , Acacia tortilis Lycium shawii, .A shrubs that were probably well established prior to current browsing levels. An additional 32 l.­ 10% consists of heavily grazed remnants ofPanicwn turgidwn and Pennisetwn diviswn grasses. These species, which grow in excess of 1 m tall in the protected zone, are all being maintained at a height of several cm. A. tortilis is the only forage species for gazelles and ibex among these four. In contrast, the protected zone is estimated to have

23.7% total cover, a five-fold difference. Under protection, A. tortilis and L. shawii both exhibit higher cover, but make up only 32% of the total cover, illustrating a large increase in the cover of other species. These species are mostly small perennial shrubs that are important as forage for the wild herbivores. Of the 21 important forage foods encountered in the alluvial fan community, 15 have a higher canopy cover in the protected zone and no species were found to have a greater cover in the unprotected zone. Cover differences in the island community type are not as striking. Although many species exhibit greater cover in the protected zone, most species were represented by coverages of less than 0.01 %. This is to be expected though because the island community is a more xeric site and biomass accumulation will be much slower. Additionally, occasional flooding may provide sufficient disturbance to inhibit establishment of many species.

Potential effects of camels on non-forage resources

Protective Cover

The effects of camels on canopy cover have implications beyond food availability. In tropical desert regions, animals require cover for protection from intense solar radiation.

This is necessary to control thermoregulation (Taylor 1969) and water loss. Furthermore, animals require cover for protection of young from predators which include wolves (Canis

33 I I lupus), red foxes (Vu/pes vulpes), golden eagles (Aquila chrysaetos) and steppe eagles (A. nipalensis) in the Ibex Reserve. This protective cover may not be as important to ibex

I which seek cover high in the rocky cliffs, but it is essential for gazelles. Gazelles were I often observed to rest in the shade ofAcacia canopies and other large shrubs to avoid the midday sun. Acacia canopy cover is much lower in the unprotected area and there is

I essentially no protective cover being provided by other plant species. Thus, adequate I protective cover, in the form of vegetation, is not available for gazelles in areas with heavy camel grazing. This may lead to increased heat stress in adults and increased predation on

I young. I I Succession It is difficult to predict community succession in this situation because we do not know

I the successional patterns. There are no areas in the reserve that have been protected from I grazing for extended periods. Therefore, although the vegetation has shown large differences in cover after 4 years it is not known if the communities are returning to their

I former structure and composition. All that can be shown is that the current assemblage of I plant species can recover from heavy grazing, at least in the short term. However, as plants continue to grow competition will inevitably increase. In the coming years, many

I species may be able to continue their growth, however some species may, as a result of I inter-specific competition, cease to persist. I Acacia tortilis, Pulicaria undulata, a large, aromatic shrub, and the large tufted - grasses, Pennisetum divisum, PanicUfn rurgidum, and Tricholaena teneriffae are species

J. 34 I I of interest because they are rapidly increasing in cover and density in both protected plant communities. However, only Acacia is an important gazelle and ibex food. The other species may be important in terms of protective cover, but, because they are experiencing no foraging pressure, could become aggressive competitors with forage species over the long term.

CONCLUSIONS AND MANAGEMENT RECOMMENDATIONS

Camels in the reserve are fed and watered supplementarily with government subsidized fodder (Dunham 1992, Habibi 1993, Robertson 1993), although this practice has been decreasing throughout the country. Supplementation has led to 2 problems in the reserve.

First, it allows for artificially high densities of camels. Second, it allows the camels to remain on the same range throughout the day - presumably camels had to periodically leave foraging areas to go to water sources - and year. Historically, this range was probably used only on a seasonal basis. Child and Grainger (1990) state that nomads grazed their livestock in the interior ranges during the winter, or wet season, and then moved to the more mesic coastal areas during the summer, or dry season. Plants are accumulating biomass for only a short period, yet high densities of herbivores are removing biomass year-round. This may prevent the flora from accumulating growth which may lead to a reduction in fitness or even possible elimination of some species.

This study has shown that exclusion of camels increases the availability of forage for gazelles and ibex, at least in the short term. However, camels may also be providing benefits. Many studies (McNaughton 1979, McNaughton 1984. DuToit 1990) have

35 shown that foraging by large herbivores may increase availability and quality of forage.

Quality is kept at a higher level because plant tissue is kept in a younger state and older,

less nutritious, fibrous tissue is not allowed to accumulate. This isespecially true of the

large tufted grasses. Furthennore, camels may help to prevent invasion and over­

accumulation of less preferred species. However, this is typically true only in moderately

browsed sites.

Wadi Matham cannot be considered a moderately browsed site. Robertson (1992)

estimated the carrying capacity for uncultivated wadis (eg. Wadi Matham) in the reserve at

2 2.1 camels Ikm • This estimate assumes that domestic livestock production is the first

priority. She then goes on to provide a recommended stocking rate of 1.5lkm2 in order to

prevent range degradation and allow wild herbivores to survive. This estimate is slightly

higher than that given by Cae et al. (1976). Camel densities in Wadi Matham are 3 to 6

times greater than this estimate. Furthennore, based on Coe et al. (1976), who studied the

relationship between herbivore density and annual precipitation in arid regions of East

Africa, The Ibex Reserve would have to receive 340 mm of precipitation per year (7 times

the current average) to support the present density camels in Wadi Matham. When

densities of camels, gazelles and ibex are considered together, it is easy to see that total

herbivore biomass is well above range carrying capacity. Furthennore, this grazing

pressure continues year round. Based on these numbers it is not likely that the range can

remain productive. Unfortunately, density of camels will be less responsive to range

degradation than that of gazelle and ibex because they are receiving supplementary feed.

I - 36 •

I I I This study suggests that current camel densities cannot be maintained without dramatic negative impacts on the forage base for wild ungulates. Therefore, in order for gazelles,

I ibex and camels to co-exist, numbers of camels should be reduced, supplemental feeding I of camels should cease and a program of adaptive, rotational grazing should be explored. I All 3 recommendations would be in accordance with the Draft Ibex Reserve Master Plan. Several of the objectives of the plan are to promote ibex and gazelle populations by

I maintaining their habitats and maintaining or enhancing the current diversity of the plant I communities. I I I; I I I

I I I - I ~ 37

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Cochran, William G. 1977. Sampling techniques, 3rd edition. John Wiley & Sons, New I York. 428 pp.

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39 J Habibi, K. and J. Grainger. 1990. Distribution and status of Nubian ibex in Saudi Arabia. , Oryx 24(3):138-142.

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• 40

( ~ .,...... -~- ,..",

, ' ~" '.- - . ~- " -_..' .--~ - ~ .' --, ~..' Skarpe. C. 1990. Shrub layer dynamics under different herbivore densities in an arid savanna, Botswana. J. AppL Ecol. 27:873-885.

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Zeuner, F. E. 1963. A history of domesticated animals. Hutchinson Pubs., London.

,~ , -II. -', 41 , Table 1. Seasonal density ofcamels in Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994. Density in summer is greater than density in autumn (P = 0.01). t Summer density- Autumn densitl Individuals/km2 ~8 ~1 j N (number of surveys) 16 8 95% Confidence interval 1.3 1.1 _ May through July b October through November

Table 2. Results of Shannon-Weaver diversity tests conducted in the alluvial fan vegetation type, Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994. Richness (# of species) Diversity index Growth form Protected- Unprotectedb Protecteda Unprotectedb Grasses 15 14 2.3 2.2 Forbs 12 12 1.0 1.7 Trees & shrubs 6 6 0.9 0.8 Dwarf shrubs 20 19 2.2 1.9 • Protected refers to the area where camels have been excluded for 4 years. b Unprotected refers to the area where camels have not been excluded.

Table 3. Results of Shannon-Weaver diversity tests conducted in the island vegetation type, Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994. Richness (# of species) Diversity index Growth form Protected8 Unprotectedb Protected- Unprotectedb Grasses 11 9 1.8 1.3 Forbs 10 13 0.9 0.8 Trees & shrubs 4 6 0.6 0.9 Dwarf shrubs 15 13 1.8 1.9 • Protected refers to the area where camels have been excluded for 4 years. b Unprotected refers to the area whcl\.! camels have not been excluded.

- 42 I

II , ,

, Table 4a. Mean density (individuals!ha) of perennial grass species in the alluvial fan vegetation type, Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994. Sample size = 60 in all cases. I Density Density t - testsf Species Protected· Unprotectedb (P - values) , Density greater in protected zone Cenchrus ciliaris 438 279 0.07 Panicum turgidum 1366 II Penn/Pane 1485 875 0.04 Pennisetum divisum 53 Stipagrostis sppe. 1539 995 0.06 II Tricholaena teneriffae 557 53 0.0004 II Density greater in unprotected zone Cynodon dactylon 743 1499 0.06 , Lasiurus scindicus 13 133 0.01 No difference in density II Chrysopogon plumulosuse 1618 2295 >0.10 Cymbopogon commutatus 371 345 >0.10 Dichanthium Joveolatum 212 265 >0.10 I Hyparrhenia hirtae 477 332 >0.10 Ochthochloa compressa 1287 716 >0.10 Oropetium/Tripo gond 172 225 >0.10 II Tetrapogon villosus 517 584 > 0.10 a Protected refers to the area where camels have been excluded for 4 years. II b Unprotected refers to the area where camels have not been excluded. C Panicwn turgidwn and Pennisetwn diviswn have been combined for comparisons, density is provided for each species separately in the protected area. d OropetiumJTripogon -- 1 of the following: Oropeliwn capense, Tripogon afrjcanus or I T. multiflorus. C Species that are important as forage for mountain gazelle and Nubian ibex. f Student's t-test based on a 2-stage cluster analyses with units 6f equal size, population variances not equal and degrees of freedom =n - 1. I ..I' 43 I Table 4b. Mean density (individualslha) of perennial dwarf shrub and vine species in the alluvial fan vegetation type, Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994. SamEle size = 60 in all cases. Density Density t-testsd Species ProtectedA Unprotectedb (P - value) Density greater in protected area Abutilon truticosumc 119 0 0.02 Anvil/ea garcinit

Density greater in unprotected area Convolvulus glomeratusC 199 279 0.07 Rhanterium epapposum 40 172 0.01

No difference in density Convolvulus hamarinensis 119 93 > 0.10 Fagonia bruguieri 4364 3263 >0.10 Gymnocarpus decandrun-{' 225 239 >0.10 H eliotrvpium ramosissimum 584 756 >0.10 Salvia aegyptiacac 729 703 >0.10 • Protected refers to the area where camels have been excluded for 4 years. b Unprotected refers to the area where camels have not been excluded.

C Species that are important as forage for mountain gazelle and Nubian ibex. d Student's t-test based on a 2-stage cluster analyses with units of equal size, population variances not equal and degrees of freedom = n - 1.

- 44 Table 4c. Mean density (individuals/ha) of perennial forb species in the alluvial fan vegetation type, Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994. Sample size = 60 in all cases. Density Density t - testsd Species Protected- Unprotectedb (P - values) Density greater in protected area Polycarpea repensc 4496 2255 0.01

Density greater in improtected area Euphorbia cf. granulata 40 1220 0.01 Haplophyllwn tuberculatwn 66 424 0.02 Polygola erioptera 13 186 0.01 Pterogaillonia calycoptera 66 451 0.01

No difference in density Boerhavia e/egans 265 292 > 0.10 Farsetia spp.c 2069 1844 > 0.10 • Protected refers to the area where camels have been excluded for 4 years. • Unprotected refers to the area where camels have not been excluded.

C Species that are important as forage for mountain gazelle and Nubian ibex. d Student's t-test based on a 2*stage cluster analyses with units of equal size, population variances not • equal and degrees of freedom =n - 1. • Table 4d. Mean density (individuals/ha) of perennial shrub and tree species in the alluvial fan vegetation type, Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994. Sample size = • 60 in all cases. II Density Density t - testsd Species Protected· Unprotectedb (P - values) Density greater in protected area - Haloxylon salicornicwnc 186 13 0.0004 No difference in density Acacia tortilisC 912 806 >0.10 - Lyciwn shaw;;" 225 '159 > 0.10 a Protected refers to the area where camels have been excluded for 4 years. b Unprotected refers to the area where camels have not been excluded. - C Species that are important as forage for mountain gazelle and Nubian ibex. II d Student's t-test based on a 2-stage cluster analyses with units of equal size, population variances not - equal and degrees of freedom = n - 1. --, 45 -I ­ I 1

Table 4e. Perennial plant species recorded in the alluvial fan vegetation type, Wadi I Matham, The Ibex Reserve, Saudi Arabia, 1994, for which mean density was estimated at less than 100 individualslha in both treatment types (protecteda and unprotected'). Because the following species were uncommon, no attempt was made to compare I densities statistically. Sample size = 60 in all cases. Grasses Forbs I Aristida adscensionis Aerva javanicac Sporoboius nervosus Cucwnis prophetarwn Echinops sp. I F arsetia burronae Reseda cf. arabica I Scorzonera tortuosissima Dwarf shrubs Trees and shrubs Astragalus sieberi Acacia ehrenbergianaC I Kohautia caespitosa Acacia raddiana Pycnocycla nodiflora Calotropis procerac c I Rhync/wsia memnonia Capparis spinosa mucronifolia Teucriwn poliwn Grewia spp.c Zilla spinosa j • Protected refers to the area where camels have been excluded for 4 years. b Unprotected refers to the area where camels have not been excluded. j C Species that are important as forage for mountain gazelle and Nubian ibex.

- .1 - 46 Table 5a. Mean density (individuals/ha) of perennial grass species in the island vegetation type, Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994. Sample size = 60 in all cases. f Density Density t - tests Species Protected& Unprotectedb (P - values) Density greater in the protected area Panicwn turgidwn 345 Penn.lPane 597 279 0.004 Pennisetwn diviswn 225 Tricholaena teneriffae 225 o 0.01

Density greater in the unprotected zone Cynodon dacty{on 106 1525 0.06 Ochthochloa compressa 40 212 0.01 OropetiumlTripogond 66 159 0.05 Stipagrostis spp.e 451 2188 0.01 • Protected refers to the area where camels have been excluded for 4 years. b Unprotected refers to the area where camels have n01 been excluded.

C Panicum turgidum and Pennisetum divisum have been combined for comparisons. density is provided for each species separately in the protected area. d OropetiumlTripogon -- 1 of the following: Oropetium capense. Tripogon a/ricanus or T. multiflorus e Species that are important as forage for mountain gazelle and Nubian ibex. I Student's t-lest based on a 2-stage cluster analyses with units of equal size. population variances not equal and degrees offreedom =n - 1.

47 Table 5b. Mean density (individuals/Ita) of perennial dwarf shrub species in the island vegetation type, Wadi Matham, The lrex Reserve, Saudi Arabia, 1994. Sample size =60 in all cases. d Density Density t - tests Species Protecteda Unprotectedb (P - values) Density greater in protected area Anvillea garcinil-c 199 80 0.01 Convolvulus glomeratusC 146 66 0.10 Fagonia bruguieri 1273 371 0.001 Pulicaria glutinosa 371 0 0.0001 Salvia aegyptiacaC 133 13 0.001

Density greater in unprotected area H eliotropium ramosissimum 159 305 0.01 Rhynchosia memnoniac 13 225 0.06 • Protected refers to the area where camels have been excluded for 4 years. b Unprotected refers to the area where camels have not been excluded.

C Species that are important as forage for mountain gazelle and Nubian ibex. d Student's Hest based on a 2-stage cluster analyses with units of equal size, population variances not equal and degrees of freedom = n - 1.

Table 5c. Mean density (individuals/ha) of perennial forb species in the island vegetation type, Wadi Matham, The lrex Reserve, Saudi Arabia, 1994. Sample size = 60 in all cases. Density Density t - testsd Species Protecteda Unprotectedb (P - values) Density greater in protected area Farselia spp.c 225 133 0.09

Density greater in unprotected area Aptosimum pumilum 13 186 0.03 Boerhavia elegans 345 570 0.08 M onsonia nivea 0 133 0.002 P o/ycarpea repensc 3064 7746 0.002

No difference in density F arsetio burlonae 146 133 >0.10 • Protected refers to the area where camels have been excluded for 4 years. b Unprotected refers to the area where camels have not been excluded.

C Species that are important as forage for mountain gazelle and Nubian ibex. d Student's t-test based on a 2-stage cluster analyses with units of equal size, population variances not equal and degrees of freedom =n - 1. - 48 Table 5d. Mean density (individualslha) of perennial shrub species in the island vegetation type, Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994. Sample size =60 in all cases. Density Density t - testsd Species Protected8 Unprotectedb (P - values) No difference in density Haloxylon salicornicumc 424 318 >0.10 • Protected refers to the area where camels have been excluded for 4 years. b Unprotected refers to the area where camels have not been excluded.

C Species that are important as forage for mountain gazelle and Nubian ibex. d Student's t-test based on a 2-stage cluster analyses with units ofequal size, population variances not equal and degrees of freedom =n - 1.

Table 5e. Perennial plant species recorded in the island vegetation type, Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994, for which mean density was estimated at less than 100 individualslha in both treatment types (protected8 and unprotected~. Because the following species were uncommon, no attempt was made to compare densities statistically. Sample size =60 in all cases. Grasses Forbs Cenchrus ciliaris Citrullus colocynthis Chrysopogon plumulosusc Cleome spp. Cymbopogon commutatus Corchorus depressus Dichanthium joveolatum Cucumis prophetarum Lasiurus scindicus Echinops sp. Sporobolus nervosus Euphorbia cf. granulata Tetrapogon villosus Haplophy/lum tubercula tum Scorzonera tortuosissima Dwarf shrubs Trees and shrubs Abutilon jruticosumc Acacia ehrenbergianaC Astragalus sieberi Acacia tortilisC Convolvulus hamarinensis Calotropis procerac Ephedra joliataC Lycium shawi{ Gymnocarpus decandrumc Ochradenus spp. Helianthemum IippiloC Kohautia caespitosa Lavandula coronopijoliac Pulicaria undulata Rhanterium epap.'1osum Rhazya stricta Tephrosia purpurea • Protected refers 10 the area where camels have been excluded for 4 years. b Unprotected refers to the area where camels have not been excluded.

C Species that are important as forage for mountain gazelle and Nubian ibex. 49 Table 6. Mean total percent canopy cover for all perennial plant species combined in 2 vegetation types, Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994. Sample size =60 in all cases. Difference between protected and unprotected is significant (P < 0.01) in both vegetation types. Alluvial fan vegetation type Island vegetation type Protected zonea 23.7% 8.9% Unprotected zoneb 5.1% 1.3% • Protected refers to the area where camels have been excluded for 4 years. b Unprotected refers to the area where camels have not been excluded.

Table 7 a. Mean canopy cover of perennial grass species in the alluvial fan vegetation type, Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994. Sample size =60 in all cases. Canopy cover Canopy cover t - testsC Species Protected8 Unprotectedb (P - values) Cover greater in protected area Cenchrus ciliaris 0.26% 0.01% 0.001 Chrysopogon plumulosui 0.60% 0.30% 0.01 Cymbopogon commutatus 0.16% 0.01% 0.02 Hyparrhenia hirtad 0.34% 0.01% 0.01 Ochthochloa compressa 0.11% 0.01% 0.004 Panicum turgidum 6.75% Penn/Panf 6.98% 0.48% 0.001 Pennisetum divisum 0.23% Stipagrostis Spp.d 0.09% 0.01% 0.01 Tricholoena teneriffae 0.46% 0.0002% 0.001 • Protected refers to the area where camels have been excluded for 4 years. b Unprotected, refers to the area where camels have not been excluded. " Panicum turgidum and Pennisetum divisum have been combined for comparisons, density is provided for each species separately in the protected area. d Species that are important as forage for mountain gazelle and Nubian ibex. e Student's t-test based on a 2-stage cluster analyses with units of equal size, population variances not equal and degrees of freedom =n - 1.

.. u 50

, ... "'"'"-,....". ~ ......

• ", ~ .;.t\,l'!:'i ,",~..:;.. • • , '. ~ ,~.~.~, ~. . Table 7b. Mean canopy cover of perennial dwarf shrub species in the alluvial fan vegetation type, Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994. Sample size =60 in all cases. Canopy cover Canopy cover t - testsd Species Protected· Unprotectedb (P - values) Cover greater in protected area Abutilon fruticosumc 0.21% 0% 0.002 Convolvulus glomeratusC 0.28% 0.001% 0.003 Convolvulus hamarinensis 0.17% 0.02% 0.03 Ephedra joliataC 0.31% 0.001% 0.01 Fagonia bruguieri 0.30% 0.01% 0.0003 Gymnocarpus decandrumc 0.13% 0.01% 0.002 Helianthemum lippit 0.09% 0.002% 0.001 Heliotropium ramosissimum 0.17% 0.001% 0.01 Hibiscus micranthusC 0.52% 0.06% 0.005 Lavandula coronopifoliac 0.57% 0.001% 0.003 Pulicaria glutinosa 1.49% 0.10% 0.001 Pulicaria unduJara 0.32% 0.004% 0.01 Salvia aegyptiacaC 0.09% 0.0002% 0.001

No difference in cover Rhynchosia memnoniac 0.13% 0% >0.10 • Protected refers to the area where camels have been excluded for 4 years. b Unprotected refers to the area where camels have not been excluded. e Species that are important as forage for mountain gazelle and Nubian ibex. d Student's t-test based on a 2-stage cluster analyses with units of equal size, population variances not equal and degrees offreedom =n • 1.

Table 7 c. Mean canopy cover of perennial forb species in the alluvial fan vegetation type, Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994. Sample size =60 in all cases. Canopy cover Canopy cover t - testsd Species Protected· Unprotectedh (P - values) Farsetia spp.c 0.44% 0.01 % 0.001 • Protected refers to the area where camels have been excluded for 4 years. b Unprotected refers to the area where camels have not been excluded.

C Species that are important as forage for mountain gazelle and Nubian ibex. d Student's t-test based on a 2-stage cluster analyses with units of equal size, population variances not equal and degrees offreedom =n - L

51

-

I ! Table 7 d. Mean canopy cover of perennial tree and shrub species in the alluvial fan vegetation type, Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994. Sample size =60 in all cases. d Canopy cover Canopy cover t - tests Species Protecteda Unprotectedb (P - values) Cover greater in protected area Acacia tortilisC 8.2% 2.9% 0.00004 Haloxylon salicornic~{ 1.18% 0.14% 0.001 Lycium shawi{' 1.21% 0.63% 0.02

No difference in cover Acacia ehrenbergianaC 0.27% 0.06% >0.10 Acacia raddiana 0.72% 0% >0.10 Grewia spp.c 0% 0.20% >0.10

& Protected refers to the area where camels have been excluded for 4 years. b Unprotected refers to the area where camels have not been excluded.

C Species that are important as forage for mountain gazelle and Nubian ibex. d Student's t-test based on a 2-stage cluster analyses with units of equal size, population variances not equal and degrees of freedom =n - 1.

Table 7e. Perennial plant species recorded in the alluvial fan vegetation type, Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994, for which mean canopy.cover was estimated at less than 0.1 % in both treatment types (protecteda and unprotected~. Because the following species were uncommon, no attempt was made to compare canopy cover statistically. Sample size =60 in all cases. Grasses Forbs Aristida adscensionis Aervajavanici Cynodon dacty/on Boerhavia elegans Dichanthium Joveolatum Echinops sp. Lasiurus scindicus Euphorbia cf. granulata Oropetium{TripogonC Polycarpea repeni Sporobolus nervosus Prerogaillonia ca/ycoptera Tetrapogon villosus Reseda cf. arabica Scorzonera tortuosissima r Dwarf Shrubs Trees and Shrubs Anvillea garcinilJ Astragalus sieberi • Teucrium polium I Zilla spinosa

& Protected refers to the area where camels have been excluded for 4 years. b Unprotected refers to the area where camels have not been excluded

C OropetiumlTripogon -- 1 of the following: Oropelium capense, Tripogon africanus or I T. multifiorus d Species that are important as forage for mountain gazelle and Nubian ibex. I 52 I

I III

l1liI Table Sa. Mean canopy cover of perennial grass species in the island vegetation type, Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994. Sample size = 60 in all cases. Canopy cover Canopy cover t - testsd IW Species Protected8 Unprotectedb (P - values) Cover greater in protected area IW Panicwn turgidwn 1.10% Penn.lPan.c 1.63% 0.08% 0.001 Pennisetwn diviswn 0.52% ~ Triclwlaena teneriffae 0.12% 0% 0.01 a Protected refers to the area where camels have been excluded for 4 years. b Unprotected refers to the area where camels have not been excluded.

~ C Panicum turgidum and Pennisetum divisum have been combined for comparisons, density is provided \ for each species separately in the protected area. d Student's t-test based on a 2-stage cluster analyses with units of equal size, population variances not , equal and degrees of freedom = n - 1.

Table 8b. Mean canopy cover of perennial dwarf shrub species in the island community type, Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994. Sample size = 60 in all cases. Canopy cover Canopy cover t - testsd Species Protected8 Unprotectedb (P - values) Cover greater in protected area Fagonia bruguieri 0.20% 0.004% 0.001 Heliolropiwn ramosissimwn 0.25% 0.002% 0.001 Pulicaria glutinosa 2.81% 0.01% 0.0001

No difference in cover Rhynchosia memnoniac 0.15% 0% > 0.10 • Protected refers to the area where camels have been excluded for 4 years. b Unprotected refers LO the area where camels have not been excluded. e Species that are important as forage for mountain gazelle and Nubian ibex. d Student's t-lest based on a 2-stage cluster analyses with units of equal size, population variances not equal and degrees of freedom =n - 1.

53 Table 8c. Mean canopy cover of perennial tree and shrub species in the island community type, Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994. Sample size = 60 in all cases. d Canopy cover Canopy cover t - tests Species Pro tecteda Unprotectedb (P - values) Cover greater in protected area Acacia ehrenbergianaC 0.43% 0.06% 0.03 Acacia tortilisC 1.24% 0.25% 0.02 Haloxylon salicornicumc 2.00% 0.54% 0.003

No difference in cover Lycium shawii" 0% 0.16% a Protected refers to the area where camels have been excluded for 4 years. b Unprotected refers to the area where camels have not been excluded.

C Species that are important a5 forage for mountain gazelle and Nubian ibex. d Student's t-test based on a 2-stage cluster analyses with units of equal size, population variances not equal and degrees of freedom =n - 1.

54 Table Sd. Perennial plant species recorded in the island vegetation type, Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994, for which mean canopy cover was estimated at less than 0.1 % in both treatment types (protecteda and unprotected~. Because the following species were uncommon, no attempt was made to compare canopy cover statistically. Sample size =60 in all cases. Grasses Forbs Chrysopogon plwnulosui Aerva javanicad Cymbopogon commutatus Aptosimwn pwnilwn Cynodon dactylon Boerhavia elegans Hyparrhenia hirtad Citrullus colocynthis Lasiurus scindicus Corchorus depressus Ochthochloa compressa Cucwnis prophetarwn OropetiwnlTripogonC Euphorbia cf. granulata Sporobolus nervosus F arsetia burtonae Stipagrostis spp.d Farsetia Spp.d Tetrapogon villosus Po/ycarpea repensd Dwarf Shrubs Trees and Shrubs Anvillea garcinil:a Calotropis proceri Convolvulus glomeratusd Ephedra /oliatad Gymnocarpus decandrwnd Helianthemwn lippil-d Kohautia caespitosa Lavandula coronopi/olii Pulicaria undulata Rhanteriwn epapposwn Salvia aegyptiacad Teucriwn poliwn Zilla spinosa

& Protected refers to the area where camels have been excluded for 4 years. b Unprotected refers to the area where camels have not been excluded c OropetiumlTripogon -- 1 of the following: Oropetium capense, Tripogon africanus or T. multiflorus d Species that are important as fOlu5e for mountain gazelle and Nubian ibex.

55 u , ,

Table 9. Above-ground biomass (kg/ha) of 4 perennial plant species important as forage for mountain gazelles and Nubian ibex in the alluvial fan vegetation type, Wadi Matham, I The Ibex Reserve, Saudi Arabia, 1994. Sample size =60 in all cases. Entries with the same letter are significantly different (P <= 0.01). Total Weight Edible Weight I Species Protected· Unprotectedb Protected· Unprotectedb Stipagrostis spp. (Grass) 3.2A 0.9A 0.7B O.IB I Rhync/Wsia memnonia (Vine) 1.4 0.9 0.4 0.2 Hibiscus micranthus (Shrub) 47.8 26.9 8.5C 1.1C Convolvulus glomeratus (Vine) 4.60 0.6D 0.9E O.IE I • Protected refers to the area where camels have been excluded for 4 years. b Unprotected refers to the area where camels have not been excluded. I I

Table 10. Above-ground biomass (kg/ha) of 3 perennial plant species important as forage for mountain gazelles and Nubian ibex in the island vegetation type, Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994. Sample size = 60 in all cases. Entries with the same letter are significantly different (P <= 0.05). Total Weight Edible Weight Species Protecteda Unprotectedb Protecteda Unprotectedb Stipagrostis spp. (Grass) 1.6A 0.5A 0.2B O.lB Rhync/Wsia memnonia (Vine) o 0.05 0.03 o Convolvulus glomeratus (Vine) 1.7C O.lC 0.2 0.1 • Protected refers to the area where camels have been excluded for 4 years. b Unprotected refers to the area where camels have not been excluded.

I

I - 56 I

I The Effects of Camels on the AvailabiJity ofAcacia tortilis Forage in The Ibex Reserve, Saudi Arabia

Abstract: The availability ofAcacia tortilis forage was examined in 4 sites (Ghaba,

Ghafar, Matham and Aima) with different intensities of browsing by camels. Camels had been excluded for 4 years from Ghaba and Ghafar, Aima experienced medium browse intensity and Matham experienced high browse intensity. Mean density ofA. tortilis did not differ among sites (P == 0.22); however trees between 0.25 and 3 m height were more abundant in Ghaba (P == 0.03) and the proportion of trees <0.25 m height was greatest in

Matham (P = 0.01). Mean canopy height and mean canopy area, for trees >0.25 m height, did not differ among the sites (P > 0.20). The density of available twigs was greater in the sites with camel browsing (P =0.003). Regression analyses, using the model: canopy area vs. available biomass of foliage, was used to relate browse intensity to available foliage.

Slopes of the resulting least squares lines were compared among the 4 sites. The assumption being that a steeper slope translates into higher yield of foliage. Aima

(medium browse intensity) had a steeper slope than those of Ghaba (P =0.01), Ghafar (P

== 0.006) and Matham (P = 0.01). Slope for Matham (high browse intensity) was steeper than that of Ghaba (P = 0.007), but it showed only marginal significance when compared to Ghafar (P = 0.09). This shows that Acacia trees browsed by camels produce more available foliage. However, camel browsing reduces the abundance ofAcacia trees in the prime forage producing class (0.25 m to 2.5 m height). This leads to more available biomass of foliage in the protected zones (P == 0.01). Camel browsing of varying intensity

57 I

has lead to variation in canopy shapes ofAcacia tortilis and this variation has lead to , I differences in the quantity of forage available to gazelle and ibex. Canopy shapes

produced by camel browsing yield a higher amount of both twigs and foliage. I I Key Words: Acacia tortilis, browse, Capra ibex nubiana, dromedary camel, Gazella I gazella, mountain gazelle, Nubian ibex, Saudi Arabia I

.. 58

~'* - .-._.

__ "....".a... '" ~ - ~.-- .~- ~~-~, ' INTRODUCTION

Large, mammalian herbivores often have marked effects on plants, one of which is the alteration of a plant's growth form. This in turn alters the quantity and quality of vegetative parts available as forage.

McNaughton (1979a, 1984) demonstrated that moderate grazing in a Serengeti grassland ecosystem creates "grazing lawns". Frequent, intense grazing causes developmental responses in grasses, the result being prostrate, low stature individuals that spread by tillering (Vesey-Fizgerald 1973a, McNaughton 1976. McNaughton 1979a.

McNaughton 1979b). Thus, a low, dense mat of grass is formed that has several benefits to herbivores. First, the plant tissue is maintained at a younger stage. This increases the quality of the forage particularly through increased concentration of nitrogen (Coppock et al. 1983, Ruess 1984, Ruess et al. 1983), Younger tissues are also more digestible

(Olubajo et al. 1974). Also, grazing lawns have a high forage mass per unit volume

(McNaughton 1984). This leads to a potentially higher food yield to herbivores per mouthful eaten. Finally, herbivory may increase above-ground productivity (McNaughton

1979a, McNaughton 1984, McNaughton 1985, Milton 1988, DuToit et al. 1990, Frank and McNaughton 1993, Gowda 1996, but see Belski 1986). Browsing can create a similar situation by producing a dense, highly branched canopy that is analogous to a grazing lawn (Vesey Fitzgerald 1973, Bergstrom 1984, McNaughton 1984, Danell and Huss­

Danell1985, Danell, Huss-Danell and Bergstrom 1985, DuToit el al. 1990, Gowda 1996).

Several studies have examined the effects of herbivores on members of the genus

Acacia. DuToit et al. (1990) demonstrated that net annual shoot extension was not

59 different between heavily browsed and unbrowsed A. nigrescens, thus showing that trees

were compensating for tissue lost to browsing. He also found that foliage in heavily

browsed A. nigrescens had higher concentrations of nutrients and lower concentrations of

condensed leaf tannins. Acacia appears to exhibit compensatory growth by increasing

shoot production and palatability after browsing (Pellew 1983, Milton 1988, DuToit et al.

1990, Gowda 1996). Pellew (1983) argues that giraffe (Giraffa came/opardalis)

browsing on Acacia increases the availability of forage. However, browsing Acacia may

not lead to an increase in availability of browse ifforage becomes less accessible due to

plant spinescence (Cooper and Owen-Smith 1986, Young 1987, Milton 1988, DuToit et

al. 1990, Milewski et aL 1991, Gowda 1996).

A. tortilis is an important dry-season forage for mountain gazelle (Gazella gazella) and

Nubian ibex (Capra ibex nubiana) in The Ibex Reserve of central Saudi Arabia (pers.

obs., Habibi 1994). During the dry season, A. tortilis is one of the few actively growing

forage plants in the reserve. A. torti/is is also the primary source of food for an abundant,

resident population of domestic camels (Came/us dromedarius). Camels, like giraffe, are

tolerant of Acacia thorns and readily consume them along with twigs and leaves. In

contrast, ibex and gazelle do not eat thoms, hence they can take twigs only to the fIrst set

of thorns (ca. 5 em) or leaves which they pick from between thorns. Year-round browsing

of A. tortilis by camels has greatly altered the canopy shape, creating spheres with a dense

mass of short twigs and thoms, somewhat analogous to a grazing lawn. The only browse

available to herbivores is therefore on the suIface of the canopy as thorns prevent them

from reaching the foliage in the inner canopy. - 60

. "-"-­ During 1990.2, large exclosures were established that excluded camels, but not gazelle. or ibex. Mter 4 years of camel exclusion, the A. tortilis trees have adopted a new shape.

They have changed from a compact, spherical shape offering a high density of relatively short shoots, into a much less compact, irregular shape that exhibits a much-reduced density of branches, which in turn are far longer than on the browsed plants. This new shape allows herbivores to reach further into the canopy when feeding. I undertook a study to measure the effects of camel browsing on the availability of A. tortilis forage for gazelle and ibex. The primary objective of the study was to relate canopy shape and browse intensity to available forage.

STUDY AREA

The Ibex Reserve is located in central Saudi Arabia 150 km southwest of Riyadh at 23 0 30'

2 N. and 460 30' E. (see Chapter 1, Fig. 1). The reserve, some 2,000 km , has a surface area of ca. 75% undulating plateau and 25% wadis (Robertson 1993). Wadis are relatively low lying areas that collect precipitation run-off from surrounding upland areas. The wadis have eroded into the upper plateau creating deep canyons with steep sided walls 100-300 m high, and the floor is typically 200-500 m wide. The study area was in the Wadi Matham watershed, including Wadis Ghaba, Ghafar and Aima (see Chapter 1, Fig. 2).

The reserve is considered a hyper-arid desert with clearly defined cool and warm seiJsons and rainfall restricted almost exclusively to the cool months, October through

April (Mandaville 1990). Mean, annual rainfall in the reserve has been estimated to be 50 mm (Habibi and Grainger 1990). Summer months, May through August, are hot with a

61 ~ daily maxima ca. 45-50° C. Winter maxima are ca. 22° C and minima average 10° C, W occasionally, dropping below 0° C. (Child & Grainger 1990). Dunham (unpubl. data)

reports the mean relative humidity near Riyadh in August 1995 was 10%. 1..1 Mandaville (1990) classifies The Ibex Reserve as within the Sudanian Plant-Geographic l.I Region. Vegetation in the reserve is found almost exclusively in the wadis.

Two indigenous and one domestic ungulate exist in the Wadi Matham watershed: l.I mountain gazelle, Nubian ibex and dromedary camels. Abundance of the 3 herbivores 1.1 differ amongst the 4 sites (Table 1). ~ Camel-proof fences were erected during 1990 at the entrances to Wadis Ghaba and

Ghafar. These fences prohibited the movement of camels, but allowed free movement by l..I gazelle and ibex. 'Therefore, Wadis Ghaba and Ghafar have been free of camel foraging U for 4 years. These camel exclusion zones provided the basis for this study. U METHODS U Sampling design

The effects of browsing by camels on Acacia tortilis were measured during the dry Ll season, October through December 1994. Four separate sites, Ghaba, Ghafar, Matham LJ and Aima, were investigated and sampling was restricted to the A. tortilis dominated LJ vegetation type. Thirty, sample points were randomly chosen in Ghaba (camels excluded)

and Matham (camels present) and 15 points in Ghafar (camels excluded) and Aima LJ

2 (camels present). Nested plots were centered on each sample point: 2 m radius (12.57 m ) LJ 2 for the trees <= 0.25 m height; 4 m radius (50.27 m ) for trees> 0.25 <= 3.0 m; and 5 m U 62 - LJ LJ 2 radius (78.54 m ) for trees > 3.0 m. Canopy height and diameter were measured on all

trees within each plot At each plot, 1 tree, the sample tree, was chosen randomly by

selecting the individual nearest to the individual nearest the sampling point. This tree was I ,. not necessarily within a plot The sample trees were used for all comparisons among sites. I Canopy dimensions were measured on all sample trees. Sample trees were then

subdivided into 8 equal parts and 1 was randomly chosen to collect data on available mass

of foliage, presence of currently growing twigs, number of unbitten twigs, and mean I length of twigs. I

I Density

Mean density ofA. tortilis was estimated for all 4 sites. All plants with>1/2 the rooted

i •, stem inside a plot were counted. Density was estimated for each plot. then from these a mean density was calculated for each site. Wilk-Shapiro rankit plots suggested that the ~I data were not normally distributed (Shapiro and Wilk 1965). Therefore, means among the , • four sites were compared by a distribution- free Kruskal-Wallis test with the null ~ hypothesis of no treatment differences. Ifsignificant differences were found, treatments ~ were compared using a distribution-free multiple comparisons test based on Kruskal­ Wallis rank sums (Dunn 1964, Hollander and Wolfe 1973). Treatments were compared at • an experiment-wise error rate of 0.20. I

- I .A 63 I I )I Canopy Dimensions W Height of trees was measured as the distance from the ground to the highest live part of

the tree. Two horizontal measures of canopy width were taken: maximum width (Xl) and ill the maximum width perpendicular to the former (X2), the limits of both measures being ill confined to living tissue (Rittenhouse and Sneva 1977). From these axes, canopy area was W estimated as the area of an ellipse: Area = 1C(xd2) * (x712). Wilk.-Shapiro rankit plots

suggested that the data were not normally distributed. Therefore, mean heights and III canopy areas were compared among sites by a distribution- free Kruskal-Wallis test with II the null hypothesis of no treatment differences. If significant differences were found.

treatments were compared using a distribution-free multiple comparisons test based on W Kruskal-Wallis rank sums. Treatments were compared at an experiment-wise error rate of III 0.20. Only individuals 0.25 m to 3 m height were compared. W

A vailability of Foliage WI Leaves available to gazelle and ibex were collected from sample trees in all 4 sites.

Leaves were considered available if they were below 1.5 m and ifI could reach them with

my thumb and forefinger. This access test was based on the assumption that my fmgers

could reach no more or no less beyond the thorns than could an ibex or gazelle. All such

"accessible" leaves were collected, oven-dried at 65° C for 24 hours and weighed.

Regression analyses were run with canopy dimensions as independent variables and

available foliage mass as the dependent variable. The best model was canopy area vs. leaf

mass. Scatter plots suggested that trees above 2.5 m height provided little available I ~ - 64 ~ I I , forage. Presumably, this is because these trees have grown out of the reach of gazelle and ibex. These trees prevented a linear relationship between canopy area and leaf mass.

I Since the proportion of trees larger than 2.5 m was low in all sites; the regression analyses I were only conducted on trees <= 2.5 m height. The resulting equations of the least I squares lines were used to predict available leaf mass for all trees. Predicted available leaf weight for all trees was summed and divided by the area sampled to estimate density of

, available leaf biomass. To determine total variance for predicted available leaf weight, the I predicted variance for each tree was summed. This value was then divided by the square , root of the total area sampled. Mean available leaf weight was then compared between the 2 sites by way of a large sample z-test for the comparison of 2 means. I Estimated Removals by Browsing - The proportion of sample trees with actively growing twigs were counted in all 4 sites. II Results were then compared using a Chi-square analyses. Twig lengths were measured on all sample trees with actively growing twigs. All twigs - were collected from the sampling subsection of a sample tree. Then, up to 5 twigs were selected at random and their lengths measured. Owing to small sample sizes in Ghaba, an -II additional 12 trees with at least 5 actively growing twigs were selected at random and data from Ghaba and Ghafar (protected areas) were combined and data from Matham and

II Aima (unprotected areas) were combined. Mean twig length was estimated for each tree. - Then, means of all trees were used to estimate mean twig length for each site. Data were ~l 65 I II asswned to be non-nonnal and therefore compared using a Mann-Whitney U, distribution free, rank sum test.

All available, unbitten twigs were counted within the sampling subsection of a sample tree. This provided an estimate of total bites available. Owing to small sample sizes, data for Ghaba and Ghafar were combined and data for Matham and Aima were combined.

Data were assumed to be non-nonnal and therefore means were compared by way of a

Mann-Whitney U, distribution free rank sum test.

Regressions

Slopes of the resulting least squares lines for the regression of canopy area vs. available leaf mass, were used as an estimate of foliage availability per site. A steeper slope implies more available foliage. Therefore, slopes were compared, according to Weisberg (1985), as a measure of camel impacts on foliage availability.

RESULTS

The data provide only a partial picture of the potential impacts of browsing by camels on Acacia tortilis. The study was conducted early in the Acacia growing season and availability measurements were taken only once. Typically, measurements for available forage biomass would be collected regularly throughout the growing season to provide an estimate of forage produced during the entire season. At the time of the study, leaf flush was complete; but twig growth was just beginning in some areas. This allowed for an

66 A vailability of Foliage

Data on available foliage biomass were collected from sites Ghaba (protected from

camel browsing) and Matham (not protected) (Table 5). Trees were divided into 2 height

classes: small trees «= 0.25 m) and large trees (> 0.25 m). Availability of foliage biomass

for small trees was relatively low and did not differ between sites (P > 0.20). Available

foliage biomass for large trees was greater in Ghaba (P =0.01).

Estimated Removals by Browsing

There was an obvious difference in the number of trees with actively growing twigs

among sites. These differences eliminated the opportunity to compare available twig

biomass among sites. All 4 sites were compared to determine the proportion of actively

growing twigs (Table 6). The 6 pairwise comparisons were analyzed using a X2 analyses.

The protected areas. Ghaba and Ghafar, did not differ nor did the unprotected areas,

Matham and Aima. Both Matham and Aima had greater proportions of trees with actively

growing twigs than Ghaba, protected area (P =0.001 and P =0.001 respectively). Aima

had a greater proportion of actively growing twigs than Ghafar (P =0.03) and the

difference between Matham and Ghafar was marginally significant (P =0.09).

Acacia trees, taller than 0.25 m, that were not protected from camel browsing, had a

greater density of available twigs (Table 7). There was a 4-fold increase in the mean

. number of twigs per tree in the unprotected zone (P =0.(03). .. 68 Twig Length

Data for mean twig length were combined to produce adequate sample sizes. Data from the 2 camel exclusion zones (Ghaba and Ghafar) were combined and data from the 2 camel browsing zones (Matham and Aima) were combined (Table 8). All trees less than

0.25 m height were deleted from the data set as was the 7.5 m tree in Ghaba. Mean twig length of A. tortilis trees was greater in the camel exclusion zone (P = 0.0004).

Regressions

Both moderate and heavy levels of browsing increased availability of foliage relative to no camel browsing; however, moderate levels of camel browsing produced the most available foliage. This can be seen by comparing the slopes of the least squares lines

(Table 9). The dependent variable is foliage mass, therefore as slope increases foliage mass increases relative to canopy area. Slopes for the 2 protected areas, Ghaba and

Ghafar, did not differ (P > 0.10). The least squares line for Aima had a steeper slope than

those of Ghaba (P = 0.01), Ghafar (P =0.006) and Matham (P =0.01). Slope for

Matham was steeper than that of Ghaba (P =0.007), but it showed only marginal

significance when compared to Ghafar (P =0.09).

DISCUSSION

Camel browsing of varying intensity has lead to variation in Acacia canopy shapes and

this variation has lead to differences in the quantity offorage available to gazelle and ibex.

69 -~

Canopy shapes produced by camel browsing yield a higher amount of both twigs and .~ foliage. j Camel browsing produces a higher density of growing points (twigs), thereby creating more potential bites. This is an effect of removing dominant, apical meristems and thus -~ allowing multiple, lateral meristems to develop. While availability of twigs, in terms of .~ biomass, could not be measured, number of available twigs is a better measure in this situation. Thoms on new A. tortilis twigs harden quickly. Gazelle and ibex will only bite .~ a twig up as far as the fIrst hardened thoms, typically less <5 cm. Therefore, they utilize ~ only the tips of twigs. Thus, to a gazelle or ibex, a short twig is as valuable as a long twig,

both represent 1 bite. Despite longer twigs in the protected zone, much of this new j growth is not utilized as forage. Given this, a growing point becomes a bite that is not j related to twig length and therefore biomass. So, density of twigs becomes a more j appropriate measure than biomass and the density of available twigs (bites) on trees> 0.25 m tall was 10 times greater in the unprotected zone. I Camels are altering canopy shape with the result that foliage is more accessible to

gazelle and ibex. By producing a higher density of branches and shortening twig internode I length, camel browsing creates a higher foliage mass per unit volume and this may lead to I a greater forage yield per bite (McNaughton 1979, DuToit et al. 1990). I Camel browsing not only increases the quantity of available forage; but it may increase

the quality of this forage. Heavy browsing by herbivores has been shown to produce I younger, less fibrous, more digestible foliage (Olubajo et al. 1974) that has a higher I nutrient concentration (Coppock et al. 1983, Ruess et al. 1983, Ruess 1984, Daneil and • I 70 I I Huss-Dane1l1985. DuToit et a1. 1990) and lower concentrations of secondary compounds

(DuToit et al. 1990).

One potential negative impact of heavy browsing on Acacias is an increase in spinescence. This may then lead to decreased forage availability. Several authors discuss spinescence as an induced defense of some plants (Cooper and Owen-Smith 1986, Young

1987. Milewski et al. 1991. Gowda 1996). Studies have shown that browsing on Acacia spp. increases thorn length and density. However, none of these studies demonstrate that the increased spinescence actually leads to a decrease in browsing. In the Ibex. Reserve, camels appear to be tolerant of thorns and have often been observed to bite through

Acacia thorns with impunity. While gazelle and ibex will not bite thorns. it would seem that they are well adapted to browsing on Acacia. Their small mouths, narrow muzzles and dexterous lips are well adapted for carefully removing foliage from between thorns.

The increased spinescence may be a strategy to protect the plants interior, therefore creating a refuge of foliage and meristematic tissue that can be quickly mobilized should browsing pressure be reduced (Vesey-Fitzgerald 1973. McNaughton 1979b). This ability to react quickly to a decrease in browsing pressure can be seen in the protected zones,

Camels may be creating a situation analogous to "grazing lawns", DuToit et al. (1990) demonstrated that impala (Aepyceros me/ampus) and giraffe (Giraffa came/oparda/is) can maintain grazing lawns in 2 species of Acacia in Africa. By doing so, they maintain a higher number of available bites (twigs) that are at a younger growth stage and therefore more nutritious and lower in concentration of tannins, When browsing was eliminated, the number of growing points and available foliage decreased dramatically.

71 ~ Although the results demonstrate that camel browsing increases the quantity of forage, ~ these measures only examine browsing effects on individual trees. To fully assess the

effects of camel browsing on the availability of forage we must also look at the availability J,I or abundance of A. tortilis trees. JpI Mean density ofA. tortilis is similar among the 4 sites. However, half of the trees in

Matham, the heavy browsing area, are <0.25 m height. In contrast, the proportion of ~ small trees is much lower in the other three sites ranging from 7 to 27% of the population. 11.1 No germination was observed during 1994 nor during the 3 years prior to the study in any

of the sites, despite flowering and seed production. Therefore, these smaller trees are not ~ new seedlings, but older trees whose growth is being arrested by heavy camel browsing. ~ When camel browsing is eliminated or reduced, these small trees are able to grow rapidly. IIrI It is the trees in the O. 25 m to 3 m height range that are producing the vast majority of available foliage. The higher density of trees in this height class in the protected area has ~ lead to a greater overall availability of foliage in the protected area. ~ Acacia trees seem to be incredibly tolerant of heavy browsing. Little mortality has

been observed in the study area and the current level of browsing pres~ure may have been ~ occurring for 20 years or more. The potential problem lies in the fact that no new trees IIJ I are being recruited into the mature tree class in Matham. Eventually, the current ~ population of mature trees will die and not be replaced. Similar situations have been I

observed in Africa (Vesey-Fitzgerald 1973, Pellew 1983a 1983b), where high densities of ILJ

giraffe are suppressing Acacia growth and preventing mature trees from entering the ~I I canopy. In Matham, Acacia trees cannot easily grow outward. Iftwigs become longer - 72 than 3 - 4 em, they are more visible and therefore more vulnerable. This means that almost all available twigs will be eaten during the growing season. The result is that most of a current season's production in Matham is removed. In contrast, trees in the other 3 sites are permitted to grow. This shows that under low to moderate browse levels,

Acacias can continue to grow and reach maturity.

This study demonstrates that browsing of Acacia tortilis can produce more available forage. However, extreme browsing pressure leads to a reduction in forage on a spatial scale by reducing the abundance of trees in the forage producing size class. Therefore, moderate levels of camel browsing may benefit gazelle and ibex. But, more research is necessary to determine the optimal stocking rates for camels in the reserve.

73 LITERATURE CITED

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Table 1. Relative abundance classifications for 3 herbivores in 4 sites in The Ibex Reserve, , Saudi Arabia, 1994. • Protected& sites Unprotectedbsites Ohaba Ohafar Matham Aima Moun tain gazelle high high medium medium Nubian ibex high high medium low Camel not present not present high medium • Protected refers to the area where camels have been excluded for 4 years. b Unprotected refers to the area where camels have not been excluded.

Table 2. Mean density (individualslha) ofAcacia tortilis by height class among 4 sites in Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994. Values with the same capital letter are si~nificantll: different (P = 0.03). Site N (plots Small trees SE Medium trees SE Large trees SE samEled) «= 0.25m) (0.25 m < x <=3 m) (> 3m) Protected& Ghaba 30 239 95 471 (A,B) 75 21 11 Ohafar 15 106 72 411 127 51 24

U nQrotectedb Matham 30 371 99 239 (A) 57 13 7 Aima 15 106 72 252 (B) 120 8 8

a Protected refers to the area where camels have been excluded for 4 years. b Unprotected refers to the area where camels have not been excluded.

Table 3. Mean height (m) of Acacia tortilis trees> 0.25 m height among 4 sites, Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994. Site Mean height SE. N Protectedft Ghaba 1.2 0.14 26 Ohafar 1.3 0.21 14

UnQrotectedb Matham 1.1 0.14 16 Alina 1.2 0.28 11 • Protected refers to the area where camels have been excluded for 4 years. b Unprotected refers to the area where camels have not been excluded.

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II 2 Table 4. Mean canopy area (m ) of Acacia tortiUs trees> 0.25 m height among 4 sites, Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994. Site Mean canopy area SE N Protecteda Ghaba 3.1 0.64 26 Ghafar 3.6 0.93 14

Unprotectedb Matham 1.9 0.39 15 Aima 2.7 1.36 11 • Protected refers to the area where camels have been excluded for 4 years. b Unprotected refers to the area where camels have not been excluded.

Table 5. Mean available Acacia tortilis foliage (kg/1m) from 2 height classes in a protected· and unprotectedb site, The Ibex Reserve, Saudi Arabia, 1994. Mean foliage mass for large trees, between the 2 sites are significantly different (P = 0.01). Site Tree height class Mean foliage mass (kglha) SE ProtectedA Small trees!: 0.4 0.7 (Ghaba) Large treesd 9.3 0.5

Unprotectedb Small treese 0.2 0.9 (Matham) Large treesd 7.7 0.4 • Protected refers to the area where camels have been excluded for 4 years. b Unprotected refers to the area where camels have not been excluded.

C Small trees = trees <= 25 em height d Large trees =trees> 25 em height but <= 2.5 m.

78 I

I Table 6. Number and proportion of Acacia tortilis trees with actively growing twigs among 4 sites in Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994. Values with the same capital letters are significantly different (P < 0.05). I Site N Number of trees with Proportion of trees with actively growing twigs actively growing twigs I Pro tecteda Ghaba 30 12 0.40 (A,B) I Ghafar 15 9 0.60 (C) Unprotectedb I Matham 30 25 0.83 (B) Aima 15 14 0.93 (A,C) I a Protected refers to the area where camels have been excluded for 4 years. b Unprotected refers to the area where camels have not been excluded. I Table 7. Mean number of twigs per Acacia tortilis tree in a site protected from camel I browsing and a site unprotected from camel browsing. All trees are > 0.25 m height. Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994. Means for the 2 sites are significantly different (P = 0.003). I Site N Mean twigs/tree SE Protected­ 28 99 33 I Unprotectedb 23 426 138 • Protected refers to the area where camels have bf,en excluded for 4 years. , b Unprotected refers to the area where camels have not been excluded.

I Table 8. Mean length (cm) of actively growing Acacia tortilis twigs in a site protected from camel browsing and a site unprotected from camel browsing. All trees are > 0.25 m height. Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994. Means for the 2 sites are I significantly different (P = 0.0004). Site N Mean twig length SE Protected· 21 9.0 1.1 I b Unprotected 17 3.5 0.5 • Protected refers to the area where camels have been excluded for 4 years. b Unprotected refers to the area where camels have not been excluded.

79 I Ii Table 9. Comparison of least squares lines among 4 sites, Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994. Site Equation of the least squares line ? P-value N II No camel browsing Ghaba y =0.02 + 11.85x 0.67 <0.001 27 Ghafar y == -0.002 + 12.88x 0.76 0.001 11 - Moderate camel browsing -­ Aima y =0.14 + 35.65x 0.67 <0.001 14

Heavy camel browsing • Math am y =0.03 + 19.76x 0.75 <0.001 29 -­

Figure 3. Proportions of height classes of Acacia tortilis among 4 sites, Wadi Matham, The Ibex Reserve, Saudi Arabia, 1994.

100% ~ f/) m80% (3 .c -C) 60% 'Q) ::r:::

o 4()01o -c o E &. 20% o 10­ 0.. O%+-- Ghaba Ghafar Matham Aima Site

8 Trees < = 25em • Trees between 25 em and 3 m 0 Trees> 3 m

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