Hippopotamus Amphibius, LINNAEUS, 1758) in Boye Wetland, Jimma, Ethiopia

Ecological behaviour of common hippopotamus (Hippopotamus amphibius, LINNAEUS, 1758) in boye wetland, jimma, ethiopia

Sefi Mekonen1*, Birnesh Hailemariam2

1. Madda Walabu University, Department of Ecotourism and Biodiversity Conservation, P.O. Box 247, Ethiopia, Email [email protected] 2. Wollega University, Department of Biology, P.O. Box 395, Ethiopia Email [email protected]

ABSTRACT

A study on the ecological behaviour of hippopotamus (Hippopotamus amphibius) was conducted in Boye wetland between February and May, 2013. The behavioural activity and event patterns were studied with 30 minutes interval following a male and female focal sampled individual. The feeding preferences of hippopotamuses determined by collecting and identifying the plant species that consumed by hippopotamus. Resting comprises the majority of their activity time with 42.50% followed by moving 34.16%, feeding 19.63% and mating 3.71%. Barking and yawning events spent 51.18% and 48.82% of their time respectively. Males spent more time only in resting records than females, while females were active in all behavioural activity and event patterns except mating activity. Feeding and moving peak activities were observed early morning and late afternoon hours with resting peak during the mid-day, while barking and yawning events were mostly increased to afternoon both in male and female hippopotamus. Hippopotamus consumed a total of 26 species of plant. Of these, Eriochloa fatmensis 11.68%, Typha latifolia 9.91%, Echinocloa pyramidalis 9.59% and Cynodon dactylon 8.45% were the top four species of plants contributing 39.63% of their overall diet.

Keywords: Behavioural activity, Boye wetland, Ecological behaviour, Feeding ecology, Hippopotamus

artiodactyls (Nowak, 1991). In reproduction INTRODUCTION behaviours of hippopotamus, females mate with the Common hippopotamus (Hippopotamus amphibius) males in the water and, 8 months gestation, 12 is the third largest herbivorous African mammal next months lactation, 4 months an oestrus; and will give to African elephant (Loxodonta africana) and birth in shallow water as well or on land (Martin, Rehinosorus (Diceros bicornis). H. amphibius is an 2005). Twins are rare; the sex ratio at birth is 1:1 unmistakable species, with a plump and thick-body, (Post, 2000). huge and round-head; great, bulk and short limbs, very large tusk-like canines, broad snout, and short- As its name suggests, the H. amphibius is an tail and short stocky legs. Their eyes, ears, and amphibious creature, which has two main habitat nostrils are placed on the high roof of the skull requirements: water to rest in during the day and (Grubb, 1993). The thin epidermis of the skin makes grass to graze on at night (Lewisson and Carter, hippopotamus vulnerable to desiccation. For 2004). The hippopotamus is found in all types of additional protection from the sun, their skin secretes permanent freshwater habitats, including ponds, a natural sunscreen substance known as “blood rivers, lakes, waterholes with gently sloping banks sweat”. Nevertheless, their skin will crack if exposed surrounded by grazing areas. It avoids extremely to air for too long due to lack of sweat glands dense swampy vegetation and fast-moving (Eltringham, 1993). waterways with rocky outcroppings (Lewson, 2007). Hippopotamus is a selective grazer consuming 35- Hippopotamus has aggressive behaviour toward 50 kg of grass or about 2.5% body weight daily people and is said to be the most dangerous of wild (Chansa et al., 2011; Théophile et al., 2012). It differs Am. J. Sci. Ind. Res., 2016, 7(2): 41-49

from other mega-herbivores in having a dual (Fig. 1). It is one of the wetlands found in this region, requirement of daily living space in water and an located about 4 km from the center of Jimma town in open grazing range (Eltringham, 1993). the East at 7° 39′38″ N and 36°52′14″ E. The current area is 110.03 hectare. The wetland is permanent Existing knowledge on hippopotamus behaviour and type with variable water level at different seasons. It ecology is still inadequate and the obtrusive and is continuously fed by ground water and/or spring often adversarial character of hippopotamus-human flow, as well as surface flow during the wet season. interactions (Dudley, 1998). These points have led to The study area receives a rainfall ranges the formulation of the objective of this study. between1416.20 and 1586.70mm per annum with an Therefore, the research on behavioural ecology of average annual rainfall of 1513.28mm having the hippopotamus in Boye wetland is crucial in its heaviest concentration from June to September. The contribution to address some of the gap areas on average maximum and minimum temperature is hippopotamus research. 27.29°C and 11.83°C respectively with a mean daily temperature of 19.56°C. MATERIALS AND METHODS

Study area: ye wetland is found in Jimma Zone of Oromiya Regional State, in southwestern Ethiopia

Fig. 1: Map of study area has also very rich macroinvertebrate taxa (Desta, Boye wetland is the areas of flat lands surrounded by 2006). small hills having dominant vegetation of Typha grasses, Sedges (Cyperacea), and some other grass Methods: Focal animal sampling method was used species. With regarding to fauna, hippopotamus and to study the diurnal activity and event patterns of a greater number of species of birds are found (Desta hippopotamuses, focusing two focal sampled and Mengistu, 2009; Mekonnen and Aticho, 2011). It individuals following the method of Altman (1974) and

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Martin and Bateson (2007) in Boye wetland between plant species was determined by sum its frequency of February and May, 2013. A pair of focal animals (an biting or feeding sign observation divided by sum of adult male and adult female) was followed and data frequency of all food plant collection at feeding sites on their diurnal activities were recorded every 30 multiplied by hundred throughout study periods (see minutes with five minutes sampling gap between equation 1) (Theophile et al., 2012). 07:00-18:00 h except 13:00-14:00 h. Focal animals were selected randomly and clearly identified by FSi CSi  100 distinctive morphological characteristics (skin mark or n ------Equation 1 skin colour) by using binoculars or naked eye. t Observations were made for five consecutive days  FS for each four months in Boye wetland. A total of 20 i1 days behavioural observation was done. n At each sampling point, the major activities of two Where  FSt = the total frequency of all individual animals were recorded separately as i1 feeding, moving, resting or standing, mating, barking collected species. and yawning. Feeding, moving, resting and mating activities were recorded as behaviour activities Data Analysis: Moreover, Statistical package (stets), while barking and yawning displays were software SPSS version 16.0 was used to analyze the recorded the frequency or events (Martin and data. Behavioural pattern variations between male Bateson, 2007; Timbuka, 2012). Events are and female were tested using t-tests. Descriptive behavioural patterns of relatively short duration such statistics were carried out to calculate frequencies, as vocalization or discrete body movements (Martin and to allow cross-tabulations. All over, 0.05 level of and Bateson, 2007), as opposed to behavioural significance used as the criterion for comparison of activities which are relatively longer duration such as the mean and confidence interval at 95%. standing, resting or feeding. RESULT The methods used to determine the feeding preferences of hippopotamuses included collecting Diurnal activity and event patterns of and identifying the plant species they consumed by hippopotamus: A total of 1368 behavioural records hippopotamus. The plant species consumed by were made from an adult male and female focal hippopotamus were studied by examination of fresh sampled hippopotamuses. Of these 647 were diurnal feeding signs that was observed from foraging area activities or stets such as feeding, moving, resting and in the crop lands during patrol early in the and mating and the rest 721 were barking and morning after the passage of the animal (Theophile et yawning events. As table 1 shown adult al., 2012). In addition to feeding sign observations, hippopotamuses were spent feeding (19.63%), the diet of hippopotamus was carried out by day time moving (34.16%), passive (lying and standing) direct feeding observation. The food plants, which (42.50%) and mating (3.71%) of their behavioural having been bitten or plucked by the animal were activities. However, 51.18% and 48.82% of collected, pressed and then identified with help of a behaviours were displayed barking and yawning taxonomist in Botanical Herbarium in Jimma events respectively. University. The percentage of feeding preference of a Table 1. Diurnal activity and event records of male and female hippopotamus Sex Behavioural Activities Total Behavioural Events Total Feeding Moving Resting Mating Barking Yawning Male 40 104 148 12 304 150 163 313 Female 87 117 127 12 343 219 189 408

Total 127 221 275 24 647 369 352 721 (19.63%) (34.16%) (42.50%) (3.71%) (51.18%) (48.82%)

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Comparison of activity and event budgets behavioural activities and events than females between male and female: Time allocated to (53.01% and 56.59%), respectively. As the figure 2 different activities and events by adult female and shown, male was spent more time for only resting male over the entire study period are provided in activity as compare to female, but mating activities table 1. Out of 647 and 721 behavioural activities and were equal for male and female, hence unfortunately events respectively, male hippopotamuses were the focal sample was selected the mating pair at display less percent (46.99% and 43.41%) of observation period.

70 60 50 40 30 20 10

Time Spent% Time 0 Feeding Moving Resting Mating Barking Yawning Male 31.5 47.04 53.82 50 40.65 46.31 Female 68.5 52.94 46.18 50 59.35 53.69

Activity and Event patterns Fig. 2: Comparison of diurnal activity and event patterns between male and female hippopotamus

A total of 48.68% of the daytime activity of the male The percentages of time spent observed for various was spent in resting. Moving was the second activities at different time of the day by male and prominent activity 34.21% followed by feeding female hippopotamus are given in figure 3. Feeding (13.16%) and mating (3.95%). Male hippopotamus and moving behavioural displays showed two peaks, was spent the barking and yawning behavioural one in the early morning between 07:00-9:00h and events 47.92% and 52.08%, respectively. Out of 343 the other in the late afternoon between 16:00 and behavioural records of the daytime activity of the 18:00 h. Resting or lying down was highly female hippopotamus, 25.36%, 34.11%, 37.03% and pronounced during the hottest parts of the day or at 3.50%, was spent in feeding, moving, resting, and noon hours started at 11:30 to 15:30h. The last mating, respectively and 53.68% and 46.32% were activity of male and female was mating. Mating of barking and yawning of the female behavioural event hippopotamus was takes place by the male climbed record. Females were spent more time feeding and to the back of the female in the water. Mating was barking than males at (t=4.211, df= 9, P=0.002 and recorded at a time between 08:00- 11:00h, 41.67% t=4.022, df= 9, P=0.003, respectively) level of and between 15:00-17:00h, 58.33% activity in both significance. Moving and yawning also higher in male and female focal sampled animals. Barking and females insignificantly (t=1.816, df= 9, P=0.103 and yawning were observed at any time of the day in both t=2.229, df=9, P=0.053, respectively). However, male and female and mostly increased at afternoon. males were spent more time resting than females, but have no statistical differences at (t=2.162, df= 9, P=0.059) level of significance.

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Feeding Moving Resting 30 Mating Barking Yawning

25 A) Male

10 Time Spent(%) Time 5

Hours of the day

Feeding Moving Resting 30 Mating Barking Yawning 25 B) Female 20

5 Time Spent(%) Time 0

Hours of the day

Fig. 3: The percentages of time spent observed for various activities and events at different time of the day by male and female hippopotamus.

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Monthly variations in activity and event budget: Table 2. List of plant species and percentage of Feeding among male hippopotamus was most the diet of hippopotamus frequent in April followed by May, whereas February Family Species Frequency Percentage and March were almost there were equivalent and of (%) the least frequent months. May was the month with observation the highest moving recorded. Moving in February and Amaranthaceae Alternanthera 6 0.63 April were equal. March recorded the highest resting nodiflora and least moving and barking frequency among male Amaranthaceae Alternanthera 4 0.42 sessilis hippopotamus. The highest barking of male Apiaceae Hydrocotyle 64 6.67 hippopotamus was recorded in April. Maximum mannii yawning was recorded in February while minimum in Apiaceae Oenanthe 9 0.94 equaled percentage in March and May. palustris Asteraceae Guizotia 10 1.04 arborescens Feeding among female was least in February than in Asteraceae Partheniuum 7 0.73 all other months, while it was at its highest in April hysterophorus followed by May. Maximum moving recorded in April Commelinaceae Commelina 23 2.40 followed by May and minimum recorded in February benghalensis Cyperaceae Cyperus 69 7.19 followed by March. Resting was higher in February rigidifolius followed by March and May and least recorded in Lamiaceae Orthosiphon 11 1.15 April. Barking along with the female hippopotamus schimperi was most frequent in February and May, closely Onagraceae Ludwigia erecta 5 0.52 followed by April. Least barking recorded in March. Onagraceae Ludwigia 3 0.31 stolonifera Maximum yawning with female hippopotamus was in Poaceae Eriochloa 112 11.68 April followed by February, while minimum yawning fatmensis was in March followed by May. Poaceae Echinocloa 92 9.59 pyramidalis Feeding ecology: A total of 26 consumed plant Poaceae Cynodon 81 8.45 dactylon species belonging to 10 families (not including crops) Poaceae Echinochloa 79 8.24 were identified (Table 2). Out of these, 14 species crus-pavonis were recorded in both feeding signs observation and Poaceae Cynodon 73 7.61 during day time feeding records in scan sample plectostachyus observation, while the remaining 12 species were Poaceae Leptochloa 72 7.51 rupestris only seen to be consumed feeding bites. The Poaceae Sacciolepis 63 6.57 contribution of the diet was from the family Poaceae Africana (38.46%), Polygonaceae (15.38%); Amaranthaceae, Poaceae Festuca 10 1.04 Apiaceae, Asteraceae and Onagraceae (7.69%, for abyssinica each), and Commelinaceae, Cyperaceae, Lamiaceae Poaceae Eleusine 9 0.94 floccifolia and Typhaceae (3.85%, for each). Based on the Poaceae Pennisetum 5 0.52 overall percentage contribution, Eriochloa fatmensis thunbergii was the most consumed plant species which Polygonaceae Persicaria 23 2.40 accounted for 11.68%. Typha latifolia ranked second decipiens Polygonaceae Persicaria 17 1.77 (9.91%), Echinocloa pyramidalis ranked third (9.59%) attenuate followed by Cynodon dactylon (8.45%) (Table 2). Polygonaceae Persicaria 9 0.94 Ludwigia stolonifera (0.31%), Alternanthera sessilis glabra (0.42%) and Pennisetum thunbergii and Ludwigia Polygonaceae Persicaria 8 0.83 erecta (0.52%, each) were the least recorded diet of senegalensis Typhaceae Typha latifolia 95 9.91 hippopotamus. Total 959 100% In addition to the species found in the wetland, Maize (Zea mays), Sugar cane (Sacchurum officinarum), Banana (Musa paradisica) and Teff (Eragristis teff) were crops observed heavily consumed by the hippopotamus in the farm land.

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DISCUSSION afternoon. This pattern is comparable to the findings of Timbuka (2012). Understanding the basic behaviors of hippopotamus will aid in the care and management of populations The percentage activity budget of male and female (Eltringham, 1999). As results of the present study hippopotamuses showed monthly differences. Water, showed, despite hippopotamus spent much of the forage close to the resting site and environmental day time in resting (42.50% ), more than half of the temperatures was the main factors which determined day time was spent performing other activities most of the activity patterns of the hippopotamus. particularly those related to moving (34.16%), feeding Feeding among both male and female hippopotamus (19.63%) and mating (3.71%). These results was most frequent in April followed by May, slightest contradict to the previous findings conducted by in February and March. In February and March the Timbuka (2012) which described more than half of temperature is highest and the rain and cloud is least. the day time hippopotamuses are resting. This So the hippopotamus spent much of the day time in difference may come from sampling techniques i.e. resting and totally submerged their body in water or the present study is conducted by focal sampled move to shaded area and mostly they didn’t need of individuals, whereas the last one survey by scan feeding. On the other hand, in the month of April the sampling. However, behavioral events or barking and day become cloudy and they become active yawning of hippopotamus had some differences day searching feeding sites and moving. Day time feeding time. activity also decreased in May because they might have obtained sufficient tender grass at night time The general activity pattern of hippopotamus was and competition with livestock also reduced, whereas characterized by morning and late afternoon peaks the feeding activity become decreased from April to with a period of rest in the middle of the day. During May. Hence, increasing of water and flood regulate the morning they spent some hours feeding, moving walking of the animal to search the food and the back to water and hence were unsettled. During the grass sink to the water (Fisher et al., 2007). hot time of the day most of them were resting. This is an important adaptation for survival and keeping their Hippopotamuses are primarily night time feeders skin from sun desiccations (Zubkowicz, 2005). At the (Lewison and Carter, 2004), results of day-time mid of the day the hippopotamus did not try to feed feeding in this study may suggest that forage is except the cloudy and rainy days. Timbuka (2012) limiting in Boye wetland. This activity of feeding might observed that hippopotamuses keep on moving and indicate that the animal had less forage during the getting into water frequently during hot days. In these previous night, possibly due to the distances between surveys the hippopotamus did not completely moved resting and foraging grounds or simply taking out from the water, this observation is also supported advantage of forage availability close to where they by Eltringham (1999) and Saikawa et al. (2004). rested in the day period. It is probable that Hence, most part of their body submersed in the hippopotamus would utilize a nearby foraging ground water and extends the neck to the grasses that fluted if available in order to meet their nutritional on the water or grow at the edge parts have to requirements (Blowers, 2008). Time used for travel forage. may influence diurnal activity budgets such as animals having to rest instead of feeding. Manteca Mating was observed only in April. The possible and Smith (1994) observed varied patterns as reasons might be mating season of hippopotamus animals had to alter their activity budget as resources came to pass before the beginning of the survey of become scarce. this study or out of sampled dates. However, hippopotamus mating usually happens within the dry The possible reasons of various frequencies of seasons (Magalhaes and Costa, 2009). In mating behavioral events of male and female hippopotamus activity male frequently walks or bathing following the might be related to the presence of disturbances, female, smelling each female’s posterior end and hunger, playing, aggressive and mating events. pushing her to shallows. Then the male climbed to Females were more aggressive and vocalized when the back of the female and mating begin. Eltringham in defense infanticide of the young offspring from the (1999) also described similar observation. Barking males or from possible disturbances. The female and yawning were observed at any time of the day in protects her calf fiercely and display barking and both male and female and mostly increased in the yawning (Eltringham, 1999; Blowers, 2008). The

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reason of highest frequency of yawning and barking peaks in morning and late afternoon with a period of records of hippopotamus in April is due to the rest in the middle of the day. Barking and yawning presence of mating (Eltringham , 1999). event patterns did not depend on the hours of the day. Moreover, barking and yawning events were displayed prominently in the dry months and due to ACKNOWLEDGEMENT competition and mating periods. This is agreement with Jones (2008) and Timbuka (2012). The courtship First and for most we would like thank God, who is often punctuated by wheeze-honking which is the made things favorable for us. We would like to extend distinctive vocalization of the hippopotamus (Jones, our sincerely and heartfelt thanks to Jimma University 2008). for providing fund to carry out the study.

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