Contributions to Zoology, 69 (3) 147-155 (2000)

SPB Academic Publishing bv, The Hague

of Jameson’s Large elapids and arboreality: the ecology green

(Dendroaspis jamesoni) in an Afrotropical forested region

Luca Luiselli¹’²,Francesco+M. Angelici¹’² & Godfrey+C. Akani³

1 DEMETRA - Institute ofEnvironmental Studies, Via dei Cochi 48/B, 1-00133 Rome, Italy, and Italian Foun-

2 dation of Vertebrate Zoology, Via Cleonia 30, 1-00152 Rome, Italy, e-mail: [email protected]; Ecology Re- search Group (NFC-FIZV), No. 4 Adak Uko Street, Calabar, Cross River State, Nigeria; department of

Biological Sciences, Rivers State University of Science and Technology, P.M.B. 5080, Port Harcourt, Rivers

State, Nigeria

Keywords: Dendroaspis jamesoni, , , ecology, Nigeria

Abstract Food habits 150

Reproductive biology 150

Discussion 151 Several mamba aspects of the ecology of Jameson’s green Acknowledgements 153 Dendroaspis jamesonijamesoni (Traill, 1843), a large-sized References 154 arboreal elapid , are studied in southern Nigeria. This

18 common and widespread in the region studied. On the basis

of the the analysis of both the habitats of capture of various specimens and the results of a logistical regression model, it Introduction seems that this species inhabits a wide variety of habitats

(including secondary forest patches and the plantation-forest One of the contextual typical corollary presence mosaic), and that its local distribution is not influencedby the

of toxic venom and size in snakes Presence of macrohabitat Green highly impressive any parameter. were in these observed in the and in the without is interest Thus, it is both dry wet season, any great public species.

statistical of bias toward a particular season. Adult sex-ratio was not surprising that, compared with most the

a females. Pproximately 1 : 1. Maleswere significantly longer than the African snake species, large-sized highly ven- All adult mamba dietary records involved warm-blooded prey omous mambas (genus Dendroaspis: Elapidae) are lizards (mainly ), whereas young mambas fed also upon well-known and relatively (e.g. see Schmidt, 1923; toads. all the adult mambas were Nearly prey eaten by lonides and arboreal, and thus for the recent Wakcman, 1955; Isemonger, 1962; there was no support hypothesis that adult mambas develop anorientationto forageon terrestrial Pitman, 1965; Lloyd, 1974; Pitman, 1974; Villiers,

. combats and observed in Male-male matings were 1975; Branch, 1988; Phelps, 1989; Angilletta, 1994; December, January, and February (dry season), and gravid Branch et ah, 1995, and references therein; Spawls females were collected in April, May, and June (wet season). and Branch, 1997). Females 7-16 and litter size was produced eggs (mean 10.9), The continuous forest zone in southern Positively correlated with maternal length. Nigeria

is inhabited by Jameson’s green mamba, Dendro-

aspis jamesoni jamesoni ( cf. Villiers, 1975; But-

Contents ler and Reid, 1986, 1990; Spawls and Branch, 1997;

Luiselli et al., 1998c), and possibly by the west- tf Abstract D. viridis 147 ern green mamba, (Villiers, 1975; Spawls

Introduction 147 and Branch, 1997). The latter species, however, Materials and methods 148 was never found by us during our long-term field

Study area 148 research in this African country (Akani et al., 1999). Data collection 148 The present paper provides detailed ecological data Analyses 148 Results 149 on the Jameson’s green mamba in southern Nige- Habitat and ecological distribution 149 ria, and compares the collected data with those Seasonal distribution of records 149 available for other large elapid snakes from Af- Population size and density 149 rica and elsewhere. Sex ratio and sexual size dimorphism 150 Akani - mamba 148 L. Luiselli, F.M. Angelici & G. C. Ecology ofJameson’s green

Materials and methods Meteorological conditions, time (Lagos time), and habitat of

each observation were recorded. Specimens found already dead

(roadkilled or machetedby farmers), including those which were Study area too damaged for any reliable body size measurement, were

inspected by dissection for data on diet and reproductive condition.

The field study was carried out mainly from September 1996 to The same was true for some preserved specimens found in

1999, with some data recorded evenearlier, in some collections of February museum (Rivers State University Port Harcourt,

localities ofsouthern These localities situated in Nigeria. were and Cross River National Park of Akampka) and in the the territories ofthe Delta Edo, and Rivers Niger (Delta, Bayelsa, laboratories ofseveral high schools and hospitals (cf. “Acknowl- in Anambra State, Abia State, Akwa-lbom State, Imo States), edgements”), where these specimens were transitorily stored to These territories in State, and Cross River State (Fig. are 1). be used for demonstration to students. Free-ranging snakes were

with ofrainforest general heavily populated, patches interspersed captured with the help of grabsticks, given the arboreal habits wide banana, among plantations (yam, cassava, cocoa, pineapple, and the extremely dangerous nature of this species which is plantain, oil palm, The forest patches have dry soil, etc.). may well-known to be highlyvenomous(Spawls and Branch, 1997),

or may be permanently or inundated earlier seasonally swamp-forests. but, contrary to reports, not very aggressive (Luiselli, Enormous extensions of formations (Avicennia mangrove marina, Akani and Angelici, unpubl. obs.). All snake specimens captured

racemosa) are found in the brackish water tracts, Rhizophora alive were palpated in the abdomen until regurgitation of the

the rivers mainly along Benin,Forcados, Ramos, Sangana, Nun, food defecation had occurred. The items ingested or prey were Saint San Brass, Nicholas, Santa Barbara, Bartholomew, identified the When the in to lowest taxon possible. prey was Sambreiro, New Calabar, Bonny, Imo, Kwa-lbo, and Cross. good condition, it was weighedby an electronic balance (to 0.1

of both environmental characteristics Much details study areas In these the measured. g precision). cases, also snake mass was and climate conditions are described elsewhere (Luiselli et al,, Voucher specimens are deposited in the herpetological collections 1998a, 1998b, 1998c). of the authors (L.L. and F.M.A., collections in Rome and in

Ikot-Ekpene, Nigeria; G.C.A., collection in Port Harcourt,

Nigeria), in the collections of the “Monti Prenestini Natural

History Museum” (Capranica Prenestina, Rome), and in the

collection ofthe Department ofBiological Sciences, Rivers State

University of Science and Technology, Port Harcourt.

Analyses

size mambas Population and density of green were estimated

by capture-mark-recapture procedures in a moist rainforest area

of southeastern Nigeria (Eket, Akwa-lbom State). The surface

of the area used for the capture-mark-recapture procedure was

100 ha. The capture-mark-recapturestudy lasted 109 days, from

early June to late September 1997. Snakes were individually

marked by ventral scale-clipping, andpainted with a white number

on the back for furtherobservations at distance without necessity

of We considered as = recaptures. “recaptures” (second sample) Fig. I. Map of Nigeria showing the study area. P.H. Port all ofthe later ofmarked individu- Harcourt city. sightings (i.e. dorsallypainted) als, when at least 10 days from the date of the first capture had

passed.

Population density was calculated by applying the Lincoln- Data collection Petersen index, with its relative 90% confidence limits (Caughley,

1977; Seber, 1982). For population size estimates, only adult

Field trips were conducted in all types of weather. Each day, specimens were considered. The Lincoln-Petersen index was the field research from 8 6 lasted approximately a.m. to p.m, used under the assumption that our mambapopulation wasnearly

(Lagos time). Night searches were done only rarely, because of without emi/immigrants. In fact, the study area is surrounded

constraints security related to the prevailing unstable political in part by a large river (Kwa-lbo River) and in part by much situation. Random routes to followed deforested that crossed locate snakes were areas, are hardly by green mambas. throughout macrohabitat every type available in each study area. The effects of the macro-environmental parameters on the

The captured snakes sexed and were measured for snout-vent presence/absence ofD. jamesoni in the study region wereassessed length (SVL, to the nearest 1 and conditional cm) tail length (tL). Since a by usinga logistic regressionmodel (forward stepwise negligibleproportion ofspecimens had the tail broken (< 0.5%), procedure) for discrete values (Hosmer and Lemeshow, 1989). for all analyses we considered the total i.e. + length, SVL tL. For this analysis, we used data ofpresence/absence ofthe green Contributions to Zoology, 69 (3) - 2000 149

mamba in 52 sites which = study were accurately surveyed during and suburban areas (« 4, 4.8%). As for the pre- our environmental works (Anonymous, 1998). The surface of served specimens observed in high school and each site was approximately 50 ha, and was separated from the hospital collections (n = 11), it was impossible to closest surveyed site by at least 10 km oflinear distance. Eight establish the habitat of capture. However, based macro-environmental parameters were identified during these

on interviews with school it is large-scale environmentalstudies (see Anonymous, 1998),and personnel, likely

for the eventual of ofthem in each of we checked presence any that these specimens came from highly disturbed the 52 sites surveyed. The designed macro-environmental pa- areas around towns (suburbia and plantations). An rameters were as follows: male in adult roadkilled was found a business part (1) primary dry forest (PDF); (2) secondary dry forest (SDF); of Port Harcourt city (“Mile two Diobu”), where (3) shrubland (SHE); (4) primary swamp-forest (PSF); (5)

farm- a few bushes and trees a wide secondary swamp-forest (SSF); (6) mangrove (MGR); (7) only surrounding land field available snakes. and plantation (FPL); (8) large waterbody (main river tract grassy were to wide or lake, PWB). The logistic regression model (-2 log likelihood The place-names, the geographic coordinates,and the macro- = 72.087; for variables not in equation: residual environmental of each of the 52 sites areomitted parameters study 2 = P = showed that X 3.5, df= 8, 0.89) thepresence m this to but in Luiselli paper save space, are fully presented ofD. was correlated with and Politano(1998). jamesoni not significantly

In macro-environmental > 0.15 in the logistic regression model, the study areas were the any parameters (P

cases = (total n 52), the presence/absence ofD. jamesoni was all cases). the and the environmental dependentvariable, parameters were

the = covariates (total n 8).

All data were statistically processed by means of a SPSS Seasonal (version with distribution of records 4.5, for Windows) personal computerpackage,

all tests being two-tailedand with alpha set at 5%.

We had 83 records of mambas for which the date

of sighting has been recorded. There was no bias

Results towards a particular season; 50.6% of the total

of = number specimens (n 83) were observed in Habitat and ecological distribution the dry season and 49.4% in the wet season

2 test P > (interseasonal difference at % with df= I,

Dendroaspis jamesoni is no doubt a common and 0.9).

in Widespread snake southeastern Nigeria: it was found in 26 of 52 sites surveyed in the eastern axis °f the Niger Delta (including sites along the courses Population size and density of the rivers Imo, Bonny, New Calabar, Sambreiro,

an d Orashi), in several sites in the Delta, Edo, Abia During a 109-day-long research period in Eket, we

a nd Imo States of adult (surroundings Aba, Okpala-Ngwa, captured and marked seven D. jamesoni (six

and in in and later five Owerri), Eket, Uyo, Ikot-Ekpene, and males and one female), recaptured

se veral sites along the Kwa-Ibo River (Akwa-lbom of these specimens (four males and the female)

State, cf. in for All the Luiselli et ah, 1998c), and Calabar, a total of eight recaptures. recaptured tu > Akampka, Oban, Ekang, Ikom, and Basua specimens exhibited sedentary habits. The female (Cross River State, cf. Butler and Reid, 1986, 1990; was contacted 23 days after the first capture in a

Schmitt, of 1996; Luiselli et ah, unpubl. data). tree adjacent to the one of capture (17 m linear We obtained 83 records of D. jamesoni for which distance), whereas the four recaptured males were the precise habitat at the point of capture has been contacted again at a mean linear distance of 26.4

■ecorded. Snakes found in from the of first and in were secondary dry forest m sites capture, two cases

11 ~ the total first 22, 26.5% of sample observed), pri- inside the same tree where they were captured.

mary = dry forest (n 10, 12%), primary swamp According to a Lincoln-Petersen index calcula-

torest = )9 = 11 = (n 22.9%), formations (n tion, population size was adults (SE 2), and ; mangrove

’ in the mosaic 0.11 adults ha' It bushy spots forest-plantation density was approximately per 1 .

~ 2,3.6%), farms and plantations (« =23,27.7%), should be noted that, given (i) the apparently sed- 150 L. Luiselli, F.M. Angelici & G.C. Akani - Ecology ofJameson’s green mamba

Table I. ofthe data collected from Jameson’s entary behaviour of these snakes and (ii) the rela- Summary dietary mambas,shorter and longer than 100 cm TL, in southeastern tive isolation of the study forest (see “Methods”), green Nigeria. For more details, see text. the Lincoln-Petersen index seems to fit well with

the < > population under study. Prey category 100 cm >100100 cm

N N

AMPHIBIA

Sex ratio and sexual size 1 0 dimorphism Bufo sp.

REPTIL1A Adult sex-ratio (males : females =1.17:1, total n 4 0 Agama agama = 63) did not differ significantly from equality

(binomial test with 1: P> 0.1). df= AVES

100 total young (< cm 0 4 Excluding specimens Dendropicos sp. (juv.)

measured the total of 22 males Cisticola 0 3 length), we length sp. (ad.)

Cisticola 0 3 and 27 females. There was considerable sexual size sp. (juv.

Passeriformes indet. 0 6 = dimorphism: the males (x= 166.4 cm, SD 25.9) Streptopelia semitorquatasemitorquata 0 I1 attained much larger sizes than the females (x = Hatchlings (undet. species) 0 5

= = 146.9 cm, SD 20.3) (Student t-test: t 2.95, df= 47, P = 0.0049). The maximum length attained MAMMALIA

males and the maximum Crocidura poensis 1 0 by was 211.5 cm, length Lemniscomys striatus 00 1 attained by females was 174.7 cm. Rodentia (indet.) I 1

Heliosciurus 00 22 Heliosciurus sp.

Scotonycteris zenkeri 00 22 Food habits

TOTAL 7 27

For dietary data 77 specimens (34 males, 29 fe-

males, 14 juveniles) were examined pooling to-

gether specimens captured alive in the field and Reproductive biology

specimens examined already dead. Identifiable food

in was found 38.2% of the males, 13.8% of the Combats betweenmales and matings were observed

females, and 28.6% of the juveniles, without any during the dry season (December, January, and

significant difference between wet and dry sea- February), both on the ground and on the trees.

2 all > in four sons (x test, in cases P 0.1). Twenty-two Combats involved two individuals cases,

of contained food in the in and specimens D. jamesoni and three individuals a single case, always

guts; however, some individuals contained occurred during the central daylight hours (11.15

than item. From shorter than Dissection of female snakes found dead one prey specimens to 15.50).

removed and 100 cm total length we 7 prey items, in the field, in bush-meat markets of local people

from specimens longer than 100 cm we removed (cf. Akani et al., 1998), and in school collections

27 items snakes did not prey (Table I). Most con- provided data on the seasonal reproductive timing

tain more than birds and females col- one prey category (i.e. and on the clutch sizes. Gravid were

mammals, or birds and , etc), but a large lected in April (n = 4), May (« = 6), and June (n =

male One 208 cm long had one squirrel (Heliosciurus 5). additional gravid female was captured in

and date. other sp.) one indetermined Passeriformes in the an unknown Adult females captured in

stomach. There between in 1 in 3 was a positive correlation periods of the year (1 February, March,

snake size in and size in log (mass, g) log prey (mass, in May, 1 in July, 1 in September, 4 November,

in = = P < g) (Spearman’s r 0.32, n 20, 0.01), and and 1 in December) were not pregnant. The small-

the variance in size increased female 119 total prey significantly est carrying eggs was cm length,

with snake size P < there (ANOVA: 0.05). and was a highly significant positive corre-

lation between maternal length and litter size (Table Contributions to Zoology, 69 (3) - 2000 151

Table II. Summary ofthe reproductive data collected fromfemale picture” of the greenmambas (D. viridis, D. angusti- Jameson’s mambas in southeastern The green Nigeria. statistics which ceps), are said to persist even in areas after of between maternal and litter the regression length size are has been forest felled, providing there are still also presented. thickets and trees to hide in (Spawls and Branch,

Parameter X SD (cm) n 1997). The same is not true for the black mamba,

D. which occurs in Female total polylepis, mainly open savan- length 145,8 cm 22.6 16 but around disturbed Range (cm) 119/ 179 nas, rarely areas (cf. Spawls

Litter size 10.9 3.11 and The 16 Branch, 1997). persistence of green mam- Range 7/16 bas in strongly urbanized areas could locally place

a serious problem to the human population, given Regression statistics: that the fate of mamba is often le- Equation; litter size = -7.89 + 0.128 x total length

2 thal and r ~ = = (Spawls Branch, 1997). 0.935; adjusted r 0.865; n 16

= = The lack of ANOVA: F= 91.13; df - 1,13; P 0.0015 interseasonal differences in the dis-

tribution of mamba sightings demonstrates that these

snakes are active the year-round, without showing II). Reproductive data the examined concerning any diapause period during the dry months. This females in are summarized Table II. We did not is not pattern general among large-sized arboreal collect data on the period of in free- egg-laying snakes of the Nigerian rainforest: in fact, it is not ranging mambas. of green However, oviposition consistent with that exhibited by Boiga blandingi four gravid specimens housed in an outdoor en- (cf. Luiselli et al., 1998b), Boiga pulverulenta, closure in Calabar (Cross River State) during 1998 Dispholicius typus, and Thrasops flavigularis (cf. occurred on 6, 16, 28 and on 22 respectively June, Angelici et al., unpublished data), but it is with July, Oviposition of should free-ranging specimens that exhibited by Rhamnophis aethiopissa (cf. most probably occur also between June and July. Angelici et al., in prep.) and Pseudohaje goldii (cf. Mamba were found in the field three eggs just Angelici et al., unpublished data). It is likely that times (24 June 1997, 14 July 1997, and 2 July 1998). the interaction of the traits “large body size” and In all cases were excavated chance from they by “arboreality” is not significantly correlated with

'roles in abandoned termite nests at forest clear- any specific annual activity pattern (all-year-round- ings. activity or dry-season-suspended-activity) in Afro-

tropical snake species.

Data on both population sizes and density of discussion mambas in Eket green could be not entirely repre-

sentative of the various populations of this spe-

on (i) the wide of the habitats of cies in southern the wide variety Nigeria, given range of Sl ghtings, (ii) the wide distribution of the species habitats inhabited by D. jamesoni, and given also ro the and the results of the lo- the study region, (iii) many problems associated with such kinds of 8>stical model regression (no macro-environmen- estimates applied to free-ranging snake populations ta' Parameter this influencing species’ presence), (cf. Parker and Plummer, 1987). Assuming that the We stress that D. is no doubt habitat jamesoni a population density of mambas in our study site and

generalist, which is well to persist that the densities of other snake very adapted many species stud- even in disturbed forest ied elsewhere and 1987 very patches, including (cf. Parker Plummer, for a Sltcs around and human towns, villages habitations. review) are at least reasonable estimates of actual 116 fact that a single specimen was found in a densities, it should be noted that D. jamesoni had

Hiongiy urbanized area of Port Harcourt city sug- a population density lower than that reported for gests that small sub-populations of Jameson’s most species. The low population density of mambas roambas can survive in small of suit- in Eket due very portions is likely to be to multiple reasons. Firstly, a 'e area (less than 2 ha In this it could be due the surface). regard, to very large size of these ar- 1e Jameson’s mamba fits well into the “general boreal clapids, as higher densities of small snakes L. F.M. & G.C. Akani - Jameson’s mamba 152 Luiselli, Angelici Ecology of green

compared with large snakes should be expected possible causes of the discrepancy between our and

(Peters and Wassenberg, 1983; Parker and Plummer, previous authors’ data sets are various. It is pos-

1987). Secondly, it could be attributable to the sible that this discrepancy depended on (i) geo-

scarcity of spatial and trophic resources availabil- graphical variation within the species, or (ii) flunk

ity, as Jameson’s mambas are syntopic with some statistical results. If hypothesis (i) is correct, it is

other large arboreal snake species, which can be likely that such geographical variation may be

related the sexual behaviour of the various potential ecological competitors (Luiselli et ah, to popu-

the Jameson’s 1998c). However, given that mamba lations of this species (see Shine, 1994a), so that

SSD (i) is a ponderous climber whose great size en- male-larger should occur in the populations

ables it to go very high in big forest trees (20-30 exhibiting male-male combats for access to females,

m or more from the ground, Luiselli et ah, unpub- whereas minor SSD should occur in the popula-

lished and has tions without such combat behaviours also observation) (ii) a cryptic green (see

colouration, it is also possible that only a relatively Shine, 1994a). In fact, combats between male D.

small portion of the individuals of the area have jamesoni have already been reported in the litera-

been marked, despite the strong field effort (on ture (Leloup, 1964), and male combat and male

man-hours and the rela- in sizes average 10 per field-day) superiority body are common among large tively long research period (109 field days). The Australian elapids (Shine, 1977, 1978; Shine and

fact that only one female was captured is intrigu- Covacevich, 1983). If hypothesis (ii) is correct,

ing but unexplicable at the present time. Based on the differences observed between our and previ- pilot telemetric studies (Angelici et ah, unpublished ous authorities’ datasets should depend on the fact

data), we suspect that the relative scarcity of fe- that we considered for our body size estimates only

males versus males depends on the fact that fe- the adult specimens, whereas these previous au-

males prefer to rest in higher strata of the forest thorities pooled together both adult and juvenile canopy, whereas males could be easily found at mambas or cited only the maximum length observed the lower branches or even on the ground. Inter- in the two sexes (cf. Schmidt, 1923; Isemonger, sexual differences in vertical utilization of the 1962; Pitman, 1974). The maximum size in our available observed also in another snake also attained males. In this space were sample was clearly by species from the Nigerian rainforest (Luiselli and case, it is obvious that our method is the more

Angelici, 1998). In any case, since no detailed data reliable, as body sizes of immature snakes depend on population densities is available for any other rather on their age than on their sex.

of Dendroaspis species, interspecific comparisons Although our records indicate that green mam- these issues be done. bas terrestrial shrews cannot According to Spawls may prey on organisms (e.g. and Branch D. from and it is clear that of their (1997), angusticeps populations toads), most preys are coastal and southern average 2-ijJ arboreal (e.g. squirrels, fruit-, birds, etc.), es- snakes per ha, but it is not clear (i) whether juve- pecially when the snakes are adults. It is also clear niles excluded from these and that of the mamba are estimates, (ii) most prey eaten by green spe- which type of statistical estimation was used to cies is warm-blooded (see also Schmidt, 1923; generate this mean density value. Wakeman, 1955; Lloyd, 1974; Pitman, 1974;

The lack of biased sex-ratio in adult Branch et green mam- Villiers, 1975; Phelps, 1989; ah, 1995, bas is consistent with data available for manyother and references therein). Moreover, our data par- snake populations studied to date, including green tially confirm Chiszar et al.’s (1994) suggestion mambas from and mambas elsewhere (Phelps, 1989) other that juvenile and adult green (D. large elapids as well (see.Shine et ah, 1996). angusticeps in the case of Chiszar et al.’s data)

As that previous authorities stated male and rely on partially different foods, with more ecto-

female Jameson’s mambas attain similar sizes thermic taken the based body prey by juveniles. However,

(Schmidt, 1923; Isemonger, 1962; Pitman, 1974), on our dietary data, we strongly agree with Branch the occurrence of it a male-larger sexual size dimor- et al. (1995) that is unlikely that adult green phism in our (SSD) populations is surprising. The mambas develop a taste for terrestrial rodents, and Contributions - to Zoology, 69 (3) 2000 153

we with Chiszar et al. (1994) that a until disagree such rity they haveattained a higher proportion of remarkable shift ontogenetic in foraging behaviour their maximum body length (Shine, 1978; 1994b). should be a widespread ecological trait in green Offspring size in D. jamesoni is unknown, but mambas. In fact, the of a to be presence few terrestrial is said possibly around 30 cm length (Spawls in adult mambas prey green (one single case and Branch, 1997). Unfortunately, we did not col- in our data: need lect Lemniscomys striatus) not infer any such small mamba from the wild (the terrestrial as the items have been smallest 58.8 foraging prey may specimen found by us was cm long, ambushed from above, or have entered trees for and in was captured late April). Thus, we cannot feeding or breeding (Branch et ah, 1995). The confirm whether the offspring size given by Spawls pattern of and prey-size/snake-size relationships exhib- and Branch (1997) is correct, we cannot es- ited by Jameson’s mambas was the tablish the of the when the “ontogenetic period year eggs actu-

shift in lower size limit” hatch. of (,sensu Arnold, 1993), ally This lack information is a hard short-

which is not uncommon among large-sized snake coming to understand the rates of growth in these

species a (for review, see Arnold, 1993). Concerning large-sized snakes. Despite direct evidence is lack- the it foraging strategy, is likely that Jameson’s ing, we suspect that rapid growth is attained in mambas exhibit a ambush mambas. fact: typical predation (see free-ranging In (i) green mambas also Angilletta, 1994, for D. angusticeps). In fact, are foundin warm climates with activity and feeding we noticed sedentary habits both in the specimens occurring year-round (see data in this paper), (ii)

102 recaptured during our capture-mark-recapture study of specimens for which data are available (in- m Eket and in the few radiotracked individuals collected and cluding specimens measured, or just monitored 1998 and 1999 of during (Angelici et al., sighted) only two (1.9% the total) were obvi- unpublished less than 70 cm This of data). ously long. scarcity very

The of small individuals that snakes strong seasonality reproductive periods suggests grow rap- exhibited Jameson’s mambas in the this of by (mating dry idly through range small body sizes, the season, and ovipositions in the wet season) mir- same being true for other large-sized elapids from rors data available for D. viridis, which is eco- elsewhere (Shine and Covacevich, 1983). However, logically similar to D. jamesoni (Phelps, 1989), considering that Jameson’s mambas are arboreal an d is found in the rainforests of western Africa and cryptically coloured, it is well possible that

(Spawls and it is the of in Branch, 1997). Moreover, likely presence very young specimens our sample that the majority of the adult females are able to of collected or just sighted records is strongly bi- reproduce every year, given that most of the fe- ased (underestimated) because of the difficulty to

males in detect such in the forest captured April-June were carrying eggs. canopy. The number of eggs produced by Jameson’s mambas ls similar to that reported for other Dendroaspis species (6-17, cf. Spawls and Branch, 1997), and Acknowledgements ls also consistent with that of the large-sized

Oxyuranus indebted several species (Shine and Covacevich, 1983), We are to companies which supported our w in In hich show continuedresearch Nigeria. particular, we extend our strong morphological, behavioural, and thanks ecological to “Agip-Petroli S.p.A.” (Milano), “Aquater S.p.A,” (S. Lorenzo convergence with African mambas in “T.S.K.J. Ltd.” (Branch Campo), Nigeria (Port Harcourt), “NAOC et al., 1995). The smallest female mamba Ltd.” (Port Harcourt), ‘‘Ecosystem s.r.l.” (Bari), “Amertex Oil to Produce was a small eggs relatively specimen and Gas Ltd.” (Lagos), “Italian Foundation of Vertebrate (119 cm total length) compared to the maximum Zoology” (Rome), and “Demetra S.p.A.” (Fano and Rome). We

s,ze attained the much pleasant time in the field with E. Politano, l.F. by species (up to 2.5 m, probably spent e v Barieenee, B. Ekeke, L.D. D. A. G. en more, cf. Otonye, Capizzi, Pazienti, Spawls and Branch, 1997). This may Paoloni,L. Rugiero, J.S. Ekanem, B. Egbide, L. Ude, L. c explained Bikikoro, by the general pattern of elapid snakes B. Bolton, C. Effah, M.A. Inyang, S. Kalio, A. Sigismondi, and 1at large species mature when they are relatively Z. Tooze: they provided us with helpful observations. The s mall (i.e at a jow r0 0rti f their maximum p p 0n 0 principals of the following colleges and hospitals are thanked

Sl2e ) of whereas smaller species tend to delay matu- forpermitting examination somepreserved specimens: Girls’ & G.C. Akani - Jameson’s mamba 154 L. Luiselli, F.M. Angelici Ecology of green

High School (Akpabuyoh), Connelia Connelly College (Uyo), Iscmongcr RM. 1962. Snakes ofAfrica. Cape Town: Books of

Government High School (Ikot-Ekpene), Federal Government Africa,

Girls’College (Abonnema),Girls’ High School (Obot-Itu), Boys’ Leloup P. 1964. Observations sur la reproduction du

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Emmanuel Hospital (Eket), and University ofCalabar Teaching Dendroaspis angusticeps. J. Herpetol. Assoc. Africa 12: 12-

Butler and thanked Hospital (Calabar), Joe Berry Hughes are 16.

for comments and of information. Dr. Annie helpful exchange Luiselli L, Akani GC, Angelici FM, Barieenee IF. 1998a.

of and Dr. Massimo Zuidcrwijk (University Amsterdam) Capula Reproductive strategies ofsympalric Bitis gabonica and Bitis

offered helpful critical comments (Zoological Museum, Rome) nasicornis (Viperidae) in the Niger Delta (Port Harcourt,

version of the on a previous manuscript. Nigeria): preliminary data. Amphibia-Reptilia 19: 223-229.

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