Amphibia: Atelopus Hoogmoedi) from Suriname: Relevant Aspects for Conservation Breeding

Natural history of Atelopus hoogmoedi

SALAMANDRA 45 4 211-218 Rheinbach, 20 November 2009 ISSN 0036-3375

Site ﬁdelity, home range behaviour and habitat utilization of male harlequin toads (Amphibia: Atelopus hoogmoedi) from Suriname: relevant aspects for conservation breeding

Martina Luger, Walter Hödl & Stefan Lötters

Abstract. Recently, neotropical harlequin toads (Atelopus spp.) have undergone drastic population declines. Captive breeding has been suggested as a way to conserve harlequin frogs threatened by the amphibian chytrid fungus and global warming. A major problem is that little is known with regard to the natural history of Atelopus species. We studied male A. hoogmoedi site fidelity, home range and habitat utilization during the long rainy season (April to August) at Brownsberg Nature Park, Suriname. Dur- ing this period, males and females occupy different habitats (i.e. streams versus forest). We studied male toads along a stream site. In total, 9 males were observed; relative abundance was 0.475 individuals per meter. Fourteen males were recaptured at the same site or its vicinity at least once and 2 maintained home ranges (38. ± 7.7 m² in size) for up to four months. However, male-male interaction was not observed. In the vicinity of streams, male A. hoogmoedi were perched 5.95 ± 36.7 cm above ground in dense understory. In conservation breeding efforts, we recommend to keep sexes separately prior to mating and to simulate the rainy season. Because males occupy home ranges at the breeding site, reproductive success in captivity may be higher when females are moved to male containers (which should have some running water imitating a stream habitat). Low male density and home range size should be considered when populating tanks with males. Tanks for males and breeding should address that wild specimens were mostly found on low vegetation. Key words. Anura, Bufonidae, ex situ conservation, habitat utilization, home range, site fidelity.

Introduction um dendrobatidis) and anthropogenic climate change have been suggested to play a Neotropical harlequin toads, genus Atelo- role (e.g. La Marca et al. 2005, Pounds et pus Duméril & Bibron, 84 (Bufonidae), al. 2006); however, others have disputed the comprise a group of more than 00 diurnal, link between climate change and outbreaks slow-moving species, which aggregate along of chytridiomycosis (Lips et al. 2008). The streams for reproduction (Lötters 996). few harlequin toads with apparently stable For almost two decades now, harlequin populations (although in IUCN Red List cat- toads have dramatically declined through- egories Vulnerable or Endangered) include out their geographic range (La Marca et al. those from eastern Central America, the low- 2005). According to the IUCN/Conserva- er eastern Andes of southern Peru and adja- tion International/NatureServe ‘Global Am- cent Bolivia, the Amazon basin and the Guia- phibian Assessment’, the genus is threatened nas (http://www.iucnredlist.org; last accessed with extinction with 8% of the species fall- 5 May 2009). ing under the IUCN Red List category Criti- Because some populations which had cally Endangered (Lötters 2007). Reasons been stable until recently are currently un- for these declines remain unknown in most dergoing dramatic declines, such as the Pan- cases, leading Stuart et al. (2004) to use the amanian Atelopus limosus Ibáñez, Jaramil- term ‘enigmatic’ declines. Among others, the lo & Solís, 995 and A. zeteki Dunn, 933 amphibian chytrid fungus (Batrachochytri- (Lips et al. 2006, K. Zippel pers. comm.), we

© 2009 Deutsche Gesellschaft für Herpetologie und Terrarienkunde e.V. (DGHT) http://www.salamandra-journal.com 211 Martina Luger et al. fear that soon the entire genus Atelopus will July, J.L. Brown pers. comm.). However, not become extinct (La Marca et al. 2005, Löt- all species of Atelopus follow these tempo- ters 2007). As advocated in the IUCN Am- ral patterns, since for example A. franciscus phibian Conservation Action Plan (ACAP), Lescure, 974 from coastal French Guiana one measure to prevent amphibian diversity (Boistel et al. 2005) and Atelopus sp. cf. spu- from irreversible loss is conservation breed- marius Cope, 874 from near Iquitos, Peru ing (Gascon et al. 2007). According to Löt- (J.L. Brown pers. comm.), reproduce during ters (2007), any Atelopus species should be the rainy season. These observations suggest considered a candidate for ex situ conserva- that tempo-spatial behaviour varies among tion. There is an urgent need for information the genus Atelopus, which is relevant for con- on natural history from the wild that can be servation breeding. applied to improve captive breeding. Only a We studied Atelopus hoogmoedi Lescure, few studies are available (reviewed in Löt- 974, a species widespread on the eastern ters 996), mainly addressing spatial and Guiana Shield with seemingly intact popula- temporal associations with a particular hab- tions (Rueda et al. 2005, Luger et al. 2008). itat. At the Monteverde cloud forest, Cos- The senior author’s preliminary observations ta Rica, Atelopus sp. (cf. varius) aggregates revealed that male A. hoogmoedi are perma- along streams during the dry season (No- nently found along small streams, while fe- vember-May) and disperses more uniformly males are encountered in forest at some dis- during the rainy season. Individuals of both tance from streams. We observed females sexes exhibit site fidelity and maintain terri- migrating to streams in January 2003, at the tories (Crump 986, 988, Pounds & Crump start of the short dry season. We studied site 989 – each as A. varius). In A. carboneren- fidelity, home range size and habitat utiliza- sis Rivero, 974 from humid forests in the tion in males of this species along a small Cordillera de Mérida, Venezuela, both sexes stream in Suriname during the rainy sea- maintain defined home ranges throughout son. Further, the relevance of our findings the year, except for the somewhat drier pe- for conservation breeding of A. hoogmoedi is riod (May to July) when individuals migrate discussed. to streams and reproduce (Dole & Durant 974 – as A. oxyrhynchus). Sexton (958) observed migrations to streams in both sexes of Material and methods A. cruciger Lichtenstein & Martens, 856 Field work from coastal forests in Venezuela during the dry season (December to March), and pro- Field work was conducted at Brownsberg posed that some male A. cruciger are pro- Nature Park, Suriname (Fig. ). Established longed residents along streams. In Panama, in 970, the park currently encompasses A. zeteki aggregate along streams from late 2,200 ha, i.e. most of Brownsberg Hill, a la- November/early December (the beginning terite range reaching 500 m elevation. The of the mating season and the transition be- area is characterized by rugged terrain with tween the wet and dry seasons) to January evergreen forested steep slopes. The climate (Karraker et al. 2006). Both sexes exhibit is seasonally tropical and humid with annual site fidelity (C. L. Richards pers. comm.), mean temperature of about 26°C and annu- with daily movements to and from elevated al bimodal rainfall of about 2,400 mm (Fitz- nocturnal sleeping positions (Lindquist et gerald et al. 2002). al. 2007). Male A. pulcher Boulenger, 882 Atelopus hoogmoedi males are commonly from Andean Peru showed site-fidelity and encountered along streams in the area dur- both sexes aggregated along streams during visits by the first author in 2003 and 2004 ing reproduction in the dry season (May to (Luger et al. 2008). We studied a population

212 Natural history of Atelopus hoogmoedi

Fig. 1. (A) Suriname with major river systems (thin black lines), Van Blommenstein Meer (grey), Pa- ramaribo (square) and location of Brownsberg Nature Park (circle). (B) Aspect of Brownsberg Nature Park with main road (bold black line) and tracks (thin black lines), headquarter (square) and creeks (thin grey lines with arrows); the location of the 1000 m² study area along the Koemboe creek where Atelopus hoogmoedi was studied is indicated by a circle. of A. hoogmoedi from 9 April to 8 August day, from 06:30-8:00 hrs, the entire plot was 2004 (47 observation days) along Koemboe surveyed for toads (i.e. in leaf litter, on fallen creek (Fig. ). This small stream, bordered tree trunks, rocks and vegetation up to 2 m with riparian forest, is located approximately above ground). Each of the 9 male individ- 2 km from the main research station of the uals encountered was weighed with a digital park (4°56’39.8” N, 55°’47.7” W; ca. 370 m mini scale (Kwang HWA e68-50, readability above sea level). The streambed is 3 m wide 0.0 g) and measured (snout-urostyle length, on average; water depth varies between 0 SUL) to nearest 0. mm using a calliper when and 80 cm. The stream gradient results in collected for the first time. Mean weight was numerous small cascades with splash zones .4 ± 0.2 g (range .-.9 g); mean SUL was and pools below. Stream banks consist of 26. ± .3 mm (range 24.-28.9 mm). sand, gravel and large boulders. Several fall- For mark-recapture purposes, the dor- en trees are found alongside and across the sal and ventral pattern of every specimen stream. The vegetation bordering the stream was photographed with a Fuji digital camera margin was mainly composed of Heliconia when encountered. Since colour patterns in sp. and other herbaceous plants such as ferns this species are constant and differ remark- and palms. Mean air temperature during the ably among individuals, individual recog- study period (taken every two hours day and nition was possible through comparison of night with four Gemini data loggers) was photographs. Capture locations were marked 23.0 ± 0.96 °C (range 20.8-27.6 °C; n = ,500); with labelled flags to estimate home range. total precipitation was ,250 mm (measured The position within the plot was taken with a continuously with an automatic rain gauge). measuring tape relative to the grid system. In Based the first author’s on preliminary addition, substrate type (leaf litter, low veg- observations on A. hoogmoedi at the study etation, rocks, logs, trees) and height above site, a 000 m² plot (25 × 40 m, with the 40 the ground were recorded for every capture m border parallel to the stream) was estab- event. lished to facilitate observations. It was divid- To determine the relationship between ed into a 5 m × 5 m grid system, which cov- () the distribution of capture locations and ered both stream banks and the forested hill habitat structures as well as between (2) the north of the stream. Every second to fourth distribution and size of home ranges and en-

213 Martina Luger et al. vironment, habitat structures occupied by Chapman 980). With this method points male A. hoogmoedi were quantified for each can be removed by their largest harmon- 5 m × 5 m square by counting individual ic mean value. Home range size (n = 8) was structures, i.e. density of understory growth correlated with an index of body condition (including herbaceous plants and palms ≥ of the toads using a Spearman rank correla- 50 cm in height and trees ≤ 3 cm diameter at tion. The index of body condition was cal- breast height), trees (> 3 cm diameter at breast culated as: body weight/SULb × 0-3 with b height), fallen tree logs (≥ 0 cm in diameter) = lg[body weight]/lg[SUL] (see Hemmer & and rocks (≥ 50 cm in diameter). In addition, Kadel 972). the slope was quantified. We chose these pa- Habitat utilization: We wanted to deter- rameters based on observations made by the mine if correlations existed between (i) cap- first author at the same study during an ear- ture locations and physiographic habitat pa- lier visit. rameters, as well as between (ii) distribution of home ranges (presence/absence) and physiographic habitat parameters. Therefore, Data analysis we quantified habitat structures, including density and position relative to the stream Site fidelity was evaluated with a recapture de- of understory growth, trees, dead wood and cay plot in the manner described by Brown & rocks. We performed two principal compo- Ehrlich (980). From the slope of the regres- nents analyses on () habitat structure data sion line in the linear area (y = .306-0.02 x, from 5 m × 5 m squares occupied by Atelo- whereas: x = natural log of the number of in- pus hoogmoedi and (2) on habitat data from dividuals in residence × days), we calculated all squares, whether occupied or unoccupied. the mean residence rate during the study pe- We used a multiple linear regression analysis riod as em, m = -0.02 (see Warren 992). This (stepwise forward) to examine which factors residence rate is an estimate of the percentage determined the distribution of occupied loca- of individuals recorded on one day that stay tions, using data only from squares in which in the area until the next observation. toads were found. Using logistic regression, Home ranges were calculated as fixed ker- we determined which habitat characteris- nels (Animal Movement 2.0 extension for tics differentiated occupied from unoccupied the ESRI GIS software ArcView; Hooge & sites. All statistical analyses were performed Eichenlaub 997). The kernel approach is with Statistica (StatSoft). a contouring method that calculates different probabilities of presence for any point within the home range of an individual (see Results Worton 989, Seaman & Powell 996). Site fidelity The contour smoothing factorh was estimated individually from the data set obtained in During our study, we in total encountered the field, according to the least square cross 9 male individuals within the 000 m² plot. validation method, LSCV (e.g. Rodgers & Three of them were observed only once and Carr 998; http://blue.lakeheadu.ca/hre). two were recaptured only once. The remain- Home ranges were computed for eight indi- ing 4 were recaptured more than one time. viduals (with ≥ 0 recaptures per individual) Along the studied stream, the relative abun- with the Animal Movement 2.0 extension for dance of male toads was 0.475 per meter. Ac- ArcView. Outliers (maximum 5% of original cording to the recapture decay plot, male At- observation points) were removed by the im- elopus hoogmoedi showed strong site fidelity plemented function Outlier Removal accord- along the stream (Fig. 2). The low decline of ing to the harmonic mean method (Dixon & the number of recaptures in the first few days

214 Natural history of Atelopus hoogmoedi

Fig. 3. Home ranges of eight male Atelopus hoog- Fig. 2. Recapture decay plot for 19 Atelopus hoogmoedi (numbered) calculated as fixed kernels moedi males between 19 April and 18 August within study plot (grid). Different isopleths border 2004. regions of equal utilization probability, i.e. the 95, 90 and 50% volume contours. Legend: t = fallen of observation indicates little migration or tree, i = island. mortality during the study period. Further- correlated factors. Concerning factor  both more, the high residence rate (0.988) sug- analyses revealed significant factor loadings gests strong site fidelity. for the variables ‘slope’, ‘distance to the stream’ and ‘density of understory growth’. With re- Home ranges gard to factor 2 this was the variable ‘trees’. Regarding the factors which determined (i) Among the eight males for which home rang- the distribution of the capture locations, we es could be computed (see Fig. 3) the mean found that they were only explained by factor size of the 95% utilization probability area  (Beta = 0.434 ± 0.67, p = 0.05; Fig. 4). Ac- (UPA) was 38. ± 7.7 m² (range 6.4-60.7 m²). cording to the logistic regression model (Fig. The 95% UPA showed overlap to some extent among some individuals (Fig. 3), whereas the activity centres (50% UPA, mean size 5.4 ± 3.4 m²; range .2-0.6 m²) almost did not overlap (Fig. 3). Spearman rank correlation revealed a significant negative correlation between home range size and body condition (95% UPA: R = -0.762, p = 0.028; 50% UPA: R = -0.786, p = 0.02; mean index of body condition .03 ± 0.). There was no correlation between residence time of individuals and the sizes of the home ranges.

Fig. 4. Multiple linear regression: correlation be- Habitat utilization tween capture locations (between 19 April and 18 August 2004 in a 1000 m² study area; see Fig. 1) and factor 1 (Beta = 0.434 ± 0.167, p = 0.015), Home range (Fig. 3) and capture locations determining the distribution of capture locations; (not shown) were non-randomly distributed. signiﬁcant factor loadings were obtained for the The two factor analyses reduced the six orig- variables slope, distance to stream and density of inal correlated habitat variables to two un- understory growth.

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vated spots up to .73 m above the ground in low vegetation (48% of the encounters). Site fidelity and the maintenance of a defined home range are considered advanta- geous since knowledge of the environment favours orientation and therefore make feed- ing more efficient; escape routes and shel- ter are easier to find (Wells 2007). In our study species, we expect that an additional reason may play a role. Male mate choice is well known in Atelopus (e.g. Lötters 996), as males try to get into amplexus with con- specific females by clasping almost anything Fig. 5. Logistic regression: correlation between that appears suitable. Females commonly ap- presence/absence of home ranges (95% UPA) of pear at the breeding sites (streams) only for eight Atelopus hoogmoedi (between 19 April and 18 August 2004) and factor 1 (significant factor purposes of reproduction. For these reasons, loadings obtained for variables slope, distance to it might be reasonable for a male to occupy stream and density of understory growth); distri- a defined home range next to a stream well bution of home ranges was determined by factor before females arrive. Interestingly, since our 1 (chi² = 25.55, p < 0.001, estimated parameter observations were made outside the breed- = -3.754 ± 1.297, t(37) = -2.895, p = 0.006). One ing season (i.e. over the long rainy season), outlier (x = 2.19; y = 1) was removed prior to we conclude that mate choice may not be the statistical analysis. only reason for maintaining home ranges. Noteworthy, it could be costly to maintain 5, Maximum Likelihood, n = 39 squares, one a large home range as evidenced by the nega- outlier removed before statistical analysis), tive correlation between sizes of home ranges presence of home ranges (ii) again were de- and body conditions of toads. termined by factor  (chi² = 25.55, p < 0.00, Maintenance of a home range during the estimated parameter = -3.754 ± .297, t(37) = rainy season in the proximity of running wa- -2.895, p = 0.006). Males were found between ter may, in some instances, even be disadvan- 0 and 73 cm above the ground (mean 5.95 ± tageous. Sudden floods, especially in canyons 36.7 cm, n = 226) in low vegetation (48% of like in the study area, can wash away Atelo- all encounters), on trees (6%), on rocks (7%) pus populations (Duellman & Trueb 986). and tree logs (5%). Only 4% of the observa- Hence, a greater perching height may be pre- tions were made in leaf litter. ferred as a mechanism to avoid this. It should also allow for an increased chance to visually locate approaching females during the mat- Discussion ing season and to attract them by calling activity. The fact that activity centres of home Male Atelopus hoogmoedi showed strong site ranges (50% UPA) almost did not overlap in- fidelity during our study period. Capture dicates that A. hoogmoedi males show territo- locations showed a clustered distribution. riality, although aggressive behaviour among Males maintained activity areas in locations males, as known in other Atelopus species covered with dense understory vegetation (Crump 988, Lötters 996) was not no- near the stream for up to four months. We ticed at all during our study. Perhaps, active found a significant negative correlation be- home range defence in A. hoogmoedi plays a tween home range size and body condition. minor role (different to home range mainte- Specimens were frequently observed at ele- nance) outside the breeding season.

216 Natural history of Atelopus hoogmoedi

Our observations on site fidelity, home References range sizes and patterns and habitat utilization in Atelopus hoogmoedi as well as the ap- Boistel, R., S. Grosjean & S. Lötters (2005): parent temporal and spatial segregation of Tadpole of Atelopus franciscus from French Guyana, with comments on other larvae of the males (and, by implication, of females) may genus (Anura: Bufonidae). – Journal of Herpe- be important for both in situ (e.g. monitor- tology, 39: 48-53. ing, population census) and ex situ (captive breeding) conservation programs. Ex situ Brown. L. & P. Ehrlich (980): Population biology of the checkerspot butterfly, Euphydryas breeding success of A. hoogmoedi at the At- chalcedona. Structure of the Jasper Ridge col- lanta Botanical Garden increased after tem- ony. – Oecologia, 47: 239-25. poral separation of the sexes prior to mating Crump, M. L. (986): Homing and site fidelity in a (R. Gagliardo, pers. comm.). This coincides Neotropical frog, Atelopus varius (Bufonidae). well with our findings. We recommend sim- – Copeia, 986: 438-444. ulating conditions of the rainy season when Crump, M. L. (988): Aggression in harlequin keeping males separated from females. Due frogs: male-male competition and a possible to the fact that males occupy home ranges at conflict of interest between the sexes. – Animal the reproductive site and that this may play Behaviour, 36: 064-077. a role in mate choice, reproductive success Dixon, K. R. & J. A. Chapman (980): Harmonic in captivity may be higher when females are mean measure of animal activity areas. – Ecol- moved to males in containers that have run- ogy, 6: 040-044. ning water for egg deposition. Low male den- Dole, J. W. & P. Durant (974): Movements and sity and home range size in the wild should seasonal activity of Atelopus oxyrhynchus (An- be considered when populating tanks with ura: Atelopodidae) in a Venezuelan cloud for- males. Besides from running water, tanks est. – Copeia, 974: 230-235. should allow toads to climb perching sites, Duellman, W. E. & L. Trueb (986): Biology of because in the wild, males were mostly found Amphibians. – New York: McGraw-Hill Pub- on low vegetation. lishing Company. Fitzgerald, K. A., B. P. E. De Dijn & M. Sutris- no (2002): Brownsberg Nature Park – Ecolog- Acknowledgements ical Research and Monitoring Program 200- 2006. – Paramaribo: Research Department of We thank K. Fiedler, C. Schulze (University of Stinasu, Foundation for Nature Conservation Vienna), T. E. Koester (University of Mainz) and in Suriname. M. Veith (University of Trier) for sharing their Gascon, C., J. P. Collins, R. D. Moore, D. R. expertise, as well as A. Amézquita (Universidad Church, J. E. McKay & J. R. Mendelson III de Los Andes, Bogotá), J. L. Brown (East Caro- (2007): Amphibian Conservation Action Plan. lina University, Greenville), R. Gagliardo (At- Proceedings: IUCN/SSC Amphibian Conser- lanta Botanical Garden), T. Halliday (The Open vation Summit 2005. – Gland: IUCN. University, Milton Keynes) and C. L. Richards Hemmer, H. & K. Kadel (972): Gewichtszustand (University of Michigan, Ann Arbor) for fruitful und Wachstumsverlauf der Kreuzkröte. – for- discussion and/or helpful comments. B. de Dijn, ma et functio, 5: 3-20. head of the Research Department of STINASU Suriname, kindly provided research permits. The Hooge, P. N. & B. Eichenlaub (997): Animal staff of Brownsberg Nature Park, especially I. Movement Extension to ArcView. Ver. .. – Molgo, helped with logistics and provided assist- Anchorage: Alaska Science Center-Biological ance in the field. Financial support of this work Science Office, U.S. Geological Survey. was through a Seed Grant by the former DAPTF Karraker, N., C. L. Richards & H. L. Ross (now IUCN Amphibian Specialist Group) and (2006): Reproductive ecology of Atelopus zeteki University of Vienna (Department of Research and comparisons to other members of the ge- Services and International Relations). nus. – Herpetological Review, 37: 284-288.

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Manuscript received: 5 May 2008 Authors’ addresses: Martina Luger, Walter Hödl, Department of Evolutionary Biology, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria; Stefan Lötters, Biogeography Department, University of Trier, 54286 Trier, Germany, E-Mail: [email protected].

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