Calloselasma Rhodostoma) in Northeast Thailand

Nest Attendance by a Female Malayan Pit Viper (Calloselasma rhodostoma) in Northeast Thailand

JACQUES G. HILL III 1*, LAWAN CHANHOME 2, TAKSIN ARTCHAWAKOM 3, KUMTHORN THIRAKHUPT 4 AND HAROLD K. VORIS 1

1 Department of Zoology, Division of Amphibians and Reptiles, Field Museum of Natural History, Chicago, IL, 60605 USA 2 Queen Saovabha Memorial Institute, Thai Red Cross Society, Bangkok, 10330, Thailand 3 Sakaerat Environmental Research Station, 1 Moo 9, Tambon Udomsap, Amphur Wang Nam Khiew, Changwat Nakhon Rachasima, Thailand 4 Department of Biology, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand

ABSTRACT.– The function of egg attendance in pit vipers is understudied and poorly understood. Temperature sensitive radio telemetry was used to study nesting behavior and body temperature in a free ranging, female Calloselasma rhodostoma, which laid and attended a clutch of three eggs at a location in northeast Thailand. Oviposition occurred between 11 and 24 August, 2004 and all eggs had hatched by October 12, 2004 (incubation period = 49-62 days). The small clutch size was probably due to small maternal body size. The nest site was a rock crevice on a rocky, north facing slope, in mature deciduous dipterocarp forest. The female apparently remained coiled around the eggs for the entire incubation period with an average body temperature (Tb) of 27.1˚C (SD=1.61, range 23.7 to 30.4, n=60). Maternal Tb was slightly higher (1.5°C) than that of an operative temperature model in a similar, nearby microhabitat, suggesting an occurrence of a small amount of maternal thermogenesis. The female fed once during incubation and underwent ecdysis at or near the time the eggs hatched. Little parental care was observed beyond the time of hatching.

KEY WORDS: nest attendance, pit viper, nest site, clutch size, body temperature, parental care

rhodostoma) is a tropical pit viper which occurs INTRODUCTION in western Laos, southern Vietnam, Cambodia, West Malaysia, Java, and most of Thailand The Malayan Pit Viper (Calloselasma (Gloyd and Conant, 1990; Orlov et al., 2002). Calloselasma rhodostoma is oviparous and one of a minority of snakes that provides parental *Corresponding author (present address): Massey University, College of Sciences, Institute of Natural care to offspring in the form of egg attendance Resources, Ecology Group, Private Bag 11 222, (York and Burghardt, 1988; Gloyd and Conant, Palmerston North, New Zealand. 1990). Little is known about the ecology of C. Tel: 64-6-356-9099 ext. 2605 rhodostoma in general and most data on nesting Fax: 64-6-350-5623 behaviour in this species come from the E-mail: [email protected] laboratory. No detailed studies of nesting 58 NAT. HIST. J. CHULALONGKORN UNIV. 6(2), OCTOBER 2006 behaviour of free ranging C. rhodostoma, or thermogenesis occurring during egg attendance other nest attending vipers, have been conducted should be investigated. Herein, we report to date and the function, costs, and benefits of observations of parental care and body this behavior are poorly understood (Shine, temperature during nest attendance in a free 1988). ranging female C. rhodostoma. Parental care is uncommon in reptiles but does occur in a variety of lizards, snakes, and crocodilians (Shine, 1988). Parental care occurs MATERIALS AND METHODS in only about 2% of oviparous squamates and has been reported in 58 snake species from 33 Study area genera. The most common form of parental care The study was conducted at the Sakaerat in snakes is “nest attendance” in which the Environmental Research Station (SERS), a 78 female remains with the eggs after oviposition hectare wildlife preserve in Nakhon Rachasima (Shine, 1988). In some snakes the parent merely Province, in northeast Thailand. Habitats at remains near the eggs but in others the maternal SERS include deciduous dipterocarp forest female coils tightly around the eggs. Nest (DDF), dry evergreen forest (DEF), and attendance presumably functions in protection of abandoned agricultural areas (see Inger and the eggs but active defence of a nest has rarely Colwell, 1977). been observed and the terms “nest guarding” or “egg-guarding” should only be applied to Radio tracking situations where active defence of the nest or The study animal was captured eggs has been confirmed through field opportunistically near the SERS compound, observation. Several species of the genus Python measured for snout-vent length (SVL) and total coil about the eggs and raise the temperature of length (TL) using a squeeze box (Quinn and the clutch above ambient through shivering Jones, 1974), and weighed ±0.1 g using a triple thermogenesis (Harlow and Grigg, 1984; Shine beam balance. Sex was determined by probing 1988). This phenomenon, termed “egg and external morphology (Gregory, 1983; brooding”, is only documented in pythons but Schaefer, 1934). The study organism was the possibility of egg brooding occurring in other surgically implanted with a 3.8 g, temperature species of snakes has rarely been tested (Shine, sensitive, radio telemeter (Holohil Systems Ltd., 1988). Some viviparous snakes also show Carp, Ontario, Canada, Model PD-2T) parental care for the young after parturition according to methods outlined in Reinert and (Shine, 1988; Greene et al., 2002). Parental care Cundall (1982). Before implantation the after parturition appears widespread among transmitter was calibrated in a water bath over viviparous viperids but it is not known if post- the range of temperatures the snake was likely to hatching parental care is provided to hatchlings encounter in the environment (10 to 40˚C at ca. in oviparous species (reviewed in Greene et al., 5˚ increments). Calibration curves explained 2002). 98.8% of the variance in transmitter Twelve viperid species are reported to temperature. The snake was held for 2 days and remain with their eggs during incubation (Shine, released at the point of capture. A Wildlife 1988). Female C. rhodostoma, and at least six Materials TRX 1000 receiver with a Yagi three- other oviparous, old world pit vipers, coil element directional antenna was used to locate closely around their eggs during incubation in a the study animal most days during the course of behavior very similar to that of egg brooding the study although there are several 3 or 4 day pythons (Gloyd and Conant, 1990; Greene et al. gaps during which field work was temporarily 2002). Because the behavior of coiling about the suspended. Multiple locations were made on eggs in C. rhodostoma is so similar to that of egg many days. We attempted to minimize brooding pythons, the possibility of disturbance to the snake during radio tracking. HILL III ET AL.– NEST ATTENDANCE BY A FEMALE MALAYAN PIT VIPER 59

Snake locations (UTM grid system) were not all of these observations are paired. SERS determined using a GPS unit and distances staff recorded relative humidity daily at 0700 between locations were calculated using simple hours local time at five locations within the planar geometry. SERS. The area within 50 m from the nest site was intensively searched by two people on September Statistical analyses 3, 2004 for the presence of other C. rhodostoma Average snake Tb was compared to Top, Tsub, to determine if communal nesting or biparental and Tair. Scores of Tb-Top, and Tb-Tair were care was occurring. The area was frequently normally distributed based on a Shapiro-Wilke searched less intensively throughout the course Test (W=0.98, p=0.66 and W=0.972, p=0.64, of the study. respectively) so a paired t-test was used to compare Tb with Top and Tair. The Top value from Temperature determinations the time nearest to that of the Tb reading was Each time the snake was relocated air used for comparison in the paired analyses. The temperature (Tair) at approximately 1 m above scores of Tb-Tsub were not normally distributed the snake was determined using a mercury bulb (W=0.920, p=0.03) so a Wilcoxon Signed Rank thermometer. Substrate temperature (Tsub) was test was used to compare Tb with Tsub. Relative also obtained from a shaded spot within 1 m of humidity values from all five locations during the the snake using a flat bulb mercury bulb incubation period were pooled for determination thermometer. The transmitter inter-pulse interval of means, variance, and ranges to give a general (IPI) was determined using stop watch or pulse idea of the relative humidity levels at SERS. interval timer for later calculation of the snake Statistical analyses were conducted using SAS body temperature (Tb). In order to determine the version 9.1 for Windows. likely Tb of a snake not exhibiting thermogenesis, in a habitat similar to the nest site, we also recorded temperature of an operative RESULTS temperature model (Top, Bakken, 1992) placed in a rock crevice near the nest site from 11 August The female study animal was captured on 19 to 9 September. The operative temperature May 2004. At the time of capture she weighed model was constructed of copper tubing (2 cm 79.2 g and was 478 mm in SVL, and 540 mm diameter, 15 cm long) painted reddish brown to TL. The 3.8 g radio transmitter (4.8 % of the match the coloration of C. rhodostoma (Bakken, total body weight of the snake) was implanted on 1992). Tubing diameter was similar to diameter 20 May. The snake did not appear to be gravid at mid-body of our study animal and tubing during processing and surgery. There were no length was approximately the width of the coiled complications with the surgery and the snake snake (Peterson et al., 1993). A Thermochron appeared healthy and active when released at the iButton (Dallas Semiconductors, Dallas, Texas, point of capture on 22 May. Her movements USA: see Angilletta and Krochmal, 2003), was after release appeared normal relative to six wrapped in aluminium hardware cloth to prevent other radio tagged C. rhodostoma at the site. the Thermochron from making contact with the On 11 July she moved to the vicinity of the side of the tubing and placed inside the tube. The location at which she would later oviposite, and remained there until 31 July, occupying three Thermochron recorded Top once per hour. Sometimes IPI was obtained remotely, different locations. She occupied a location under without making observations on the snake or a large, flat rock 4 m from the future nest site from 11 July until 28 July. Scratches in the earth recording Tsub or Tair and on some occasions equipment failures made obtaining IPI data surrounding the rock crevice were observed on impossible. For these reasons there are unequal 13 July and indicate a mammalian predator may have unsuccessfully attempted to predate the numbers of observations of Tb, Tsub, and Tair and 60 NAT. HIST. J. CHULALONGKORN UNIV. 6(2), OCTOBER 2006

FIGURE 1. Photograph of the rock crevice nest site of female Calloselasma rhodostoma at Sakaerat Environmental Research Station, Nakhon Rachasima Province. study animal. She was observed approximately surface visible never exceeded approximately 50 meters away from the future nest site on 3 20%. The snake’s head was always oriented August and arrived at the actual nest site by 11 toward the opening of the crevice and the body August. The presence of eggs was not confirmed position varied little from day to day. until 24 August 2004 though oviposition may One egg had hatched by 10 October 2004 have occurred some time prior to this. The eggs and the hatchling snake was observed lying on were difficult to see because the snake was the coiled mother. On the morning of 12 October coiled around them. Clutch size was not the remaining two eggs had hatched and all the determined with certainty until the eggs hatched snakes had left the nest. Three egg shells and the hatchlings had left the nest. remained in the nest and were collected. We The nest was located in a mature, deciduous were unable to find the hatchlings and the dipterocarp forest, on a rocky, north facing slope mother was found 58 m from the nest site. (Fig. 1). The clutch was located in a crevice The female was collected on 1 November formed by two rocks which were leaning against for removal of the radio transmitter and post- each other forming an A-shaped cavity. The radio tracking processing as the life expectancy opening of the cavity was approximately 30 cm of the radio transmitter battery was coming to an across at the bottom and 13 cm in height and was end. After defecation and removal of the radio partially obstructed by dead twigs and leaf litter. transmitter on 21 November she weighed 83.0 g The eggs were in contact with a dry soil and measured 52.5 cm SVL and 59.0 cm TL. substrate. She had grown 3.8 g in weight, 4.7 cm in SVL, A total of 61 visual observations were made and 5.0 cm in TL over the 165 day radio on the snake on 56 days during nest attendance. tracking period. On every occasion the snake was coiled about the eggs. The extent to which the eggs were Feeding and ecdysis exposed varied slightly but the amount of egg HILL III ET AL.– NEST ATTENDANCE BY A FEMALE MALAYAN PIT VIPER 61

The female snake was observed with food The timing of reproductive activities of C. lumps in her gut on 4 October, and 1 November. rhodostoma vary across the species range The 4 October observation was made towards (Daltry, 1995; see Table 1). Apparently, mating the end of the incubation period. The 1 is initiated by the start of rains, after a period of November observation was made after the eggs aestivation during the dry season (Gloyd and had hatched and she had moved away from the Conant, 1990). Rainy season starts in April or nest site. She had shed by October 12, very close May in eastern Thailand, southern Laos, and to the time that the eggs hatched. Cambodia, in February or March in peninsular Thailand, and in October and November in Java Body temperatures and environmental (Daltry, 1995). Daltry (1995) reports that mating variables coincides with onset of the rainy season in each The female had an average Tb of 27.1 ˚C of the above mentioned areas, but little data exist (SD=1.62, range 23.7 to 30.4˚C, n=60) during on the subject (Table 1). Data on timing of the period of nest attendance. Tair averaged oviposition and hatching also vary across the 28.0˚C (SD=1.9, range 25.0 to 32.8, n=36) range of C. rhodostoma and no clear patterns are while Tsub averaged 28.5˚C (SD=1.9, range discernable (Table 1). 26.0 to 34.5, n=38). Top under a rock in the Our data on timing of reproduction differ vicinity of the nest site averaged 25.2˚C from several other reports from Thai C. (SD=1.1, range 23.0 to 30.0, n=880). rhodostoma (Table 1). Most of these data come Tb was an average of 1.5 ˚C warmer than from captive snakes (eg. Chanhome, 1998; simultaneous Top based on a paired t-test Chanhome et al. 2001; Werler, 1970) which may (t=11.82, p < 0.0001, n=46). Average Tb was not reflect behavior in free ranging animals but 1.8 ˚C cooler than simultaneous Tair (t=-7.59, Purananda (1957) reports that C. rhodostoma p<0.0001) and was also significantly cooler “north of Prachuap” oviposite in May while than simultaneous Tsub by 2.1˚C based on a those in peninsular Thailand do so in August. Wilcoxon’s Signed Rank test (S=-232.5, Callselasma rhodostoma in Laos (Deuve, 1970) p<0.0001). The maximum difference between are reported to oviposite in June and July which our female’s Tb and Top was 3.4˚C. All the differs from the snakes at SERS. More data on largest positive differences we observed between timing of reproduction in C. rhodostoma across Tb and Top occurred in the late afternoon and the range are needed. early evening when Te was dropping. Relative humidity at SERS averaged 86.9% (SD=5.3, Incubation period range 74 to 98, n=460) during the incubation The incubation period of 48 to 62 days period. observed for C. rhodostoma in this study is comparable to, but somewhat longer than, other DISCUSSION reported incubation periods for the species (Table 1). Even the minimum possible Timing of oviposition, hatching, and incubation period for our observed clutch, 49 mating days, is still the longest reported for the species. Our data on one female support an August The incubation period we observed may have oviposition period and an October hatching time been longer than those observed for captive for C. rhodostoma at SERS in northeast clutches because environmental conditions in the Thailand. Mating was not observed. Male C. laboratory may have been more favourable for rhodostoma engage in combat rituals during development of the young. Our data may mating (York, 1984) and this was not observed represent a more realistic estimate of incubation in any of the three males we radio tracked so period for free ranging C. rhodostoma in mating may have preceded the initiation of our northeast Thailand. study. 62 NAT. HIST. J. CHULALONGKORN UNIV. 6(2), OCTOBER 2006 Reference

Present Study Chanhome et al., 2001 York & Burghardt, 1988 Werler, 1970 Smith, 1915 Purananda, 1957 Purananda, 1957 Chanhome, 1998 Bulian, 2003 Deuve, 1970 Daltry, 1995 Bergman, 1961 Kopstein, 1938 Daltry, 1995 Gloyd & Conant, 1990 F F F F F F F C C C C C F? F? F/C Study Type Study Type

SVL SVL 264 g 540mm mm TL 702-794 802 mm Maternal Body Size Body 773 mm TL

? ? ? ? 1 4 1 1 1 1 1 4 1 1 Clutches Number of

3 “ 27 14 13 17 31 22 22 17-29 20-40 25-35 19-29 Clutch size . Study type: F = field study, C = data from captive snake(s)

“ 37 47 28 49-62 37-46 39-40 Incubation Period (days) Calloselasma rhodostoma

Aug. 8-Jun 26-Jul 30-Jun Oct. 13 of rainy Time of Hatching 10-12 Oct. “beginning

May Eggs Aug. Aug. Aug. 5 Sept. 5 1 Sept. 11 – 24 24-May Time of collected June –July Ovipositio June - July July –Aug. Feb.- Mar.

April Mating Time of Oct.-Nov. Feb.-Mar. . Summary of literature on reproductive biology Locality 1. ABLE T NE Thailand Central Southern and & Thailand (Pitsanoluk?) Thailand Thailand Thailand Thailand “north of Prachuap” Peninsular Thailand Peninsular Thailand Peninsular Thailand Laos W. Malaysia West Java West Java West Java ?

HILL III ET AL.– NEST ATTENDANCE BY A FEMALE MALAYAN PIT VIPER 63

Clutch size observed a C. rhodostoma in Surathani, Thailand The clutch size of three observed in this nesting in an open area, on moist soil, in grass study is by far the smallest reported for this about 40 cm tall. species (Table 1). Calloselasma rhodostoma The rock crevice used by our female for typically produce clutches of 17 to 40 eggs but nesting would clearly provide physical protection all reports of clutch size which include maternal for the parent and the eggs and would also body size indicate maternal females were over prevent visual detection of the clutch from the 700 mm TL (Table 1). Our female was above. Raptors prey on C. rhodostoma at SERS considerably smaller (79.2 g, 540 mm TL) than (J. Hill, personal observation) and the rock the snakes in all of the above accounts. For crevice would provide protection against avian example a 264 g C. rhodostoma produced a predators. The rock crevice nest site was clutch of 31 eggs in southern Thailand (Bulian, probably easily defended by active means. Our 2003). The relationship of female body size to study animal kept her head oriented in the clutch size has not been well studied for C. direction of the crevice opening, making it rhodostoma but the small clutch size observed in difficult for an animal to predate the eggs this study may be attributable to small maternal without sustaining a bite from the venomous body size. Brood size is generally correlated to parent. Scratch marks on the ground at the female body size within each snake species opening to different rock crevice occupied by although exceptions to this trend exist (Shine, our female while she was gravid indicate that she 1977; Fitch, 1970). The smallest gravid female may have survived an attack from a predator in a C. rhodostoma found in a study in Jakarta was location very similar to the nest site. Pit vipers 648 mm SVL (Bergman, 1961). Gloyd and which coil around their eggs probably actively Conant (1990) consider C. rhodostoma larger defend them when necessary and their nesting than 300 mm TL to be “non-juvenile” but they behavior is probably best described as “nest provide no justification for this. Bergman (1961) guarding” (Shine, 1988). considered female C. rhodostoma to be adult at York and Burghardt (1988) assumed that C. approximately 452 mm TL. Calloselasma rhodostoma laid eggs on the ground without rhodostoma at SERS appear to be somewhat cover and that the coiling female provided smaller than those found further south in the passive defence of the clutch by virtue of her species range (J. Hill, in preparation). camouflaged body. The benefit of protection of the clutch through crypsis would be limited for Nest site and benefits of nest attendance snakes nesting in such protected locations but Our study provides the first report of C. might prevent visual detection of the clutch from rhodostoma nesting in a rock crevice (Figure 1). a predator on the ground peering into the Existing data on nesting locations are limited but crevice. Protection of the clutch by crypsis is C. rhodostoma appears to utilize a variety of probably important for C. rhodostoma nesting in microhabitats for nesting. Calloselasma less sheltered areas. rhodostoma generally nest above ground, in Several reports exist for biparental care in humid, shady spots, (but not saturated ground), pit vipers, in which the males attend to the eggs including log piles, long grass, junk piles, and with females (Deuve, 1970; Manthey and beneath houses (J. Daltry, pers. com.). Grossman, 1997). We searched the vicinity of Callosesma rhodostoma in Laos nested in the nest extensively and found no other snakes, sheltered holes, often at the foot of banana trees, so it is unlikely that biparental care took place. in sandy soil, covered with dry leaves, and Previous reports of biparental care may be exposed to the sun (Deuve, 1970). Three C. erroneous (Shine, 1988). Lack of conspecific rhodostoma nests in southern Thailand were females in the nest site vicinity indicates nesting “positioned in fairly sheltered localities, but were was not communal in this instance. Communal not covered” (Leakey, 1969). Bulian (2003) 64 NAT. HIST. J. CHULALONGKORN UNIV. 6(2), OCTOBER 2006 nesting occurs in a number of other crotalines a clutch of eggs (Van Mierop and Barnard, (Greene et al., 2002). 1976). The small average difference between Tb Coiling around the clutch probably also and Top could have been due to slight temperature serves to regulate the egg’s exposure to variations between microhabitats but we cannot moisture. Maternal coiling around the eggs in rule out the possibility of small amount of heat Python regius substantially decreased desiccation being generated by the coiling snake. Tb was of the eggs relative to non-brooded eggs and probably cooler than both Tair and Tsub because maternally brooded neonates were larger, all measurements of Tsub and Tair were taken heavier, and had longer jaws than non-brooded during the day between 09:00 and 17:00 at neonates (Aubret et al. 2005). A captive, egg which time temperatures in the rock crevice were attending C. rhodostoma varied the degree to probably cooler than ambient due to lack of which the eggs were exposed in response to exposure to sunlight. relative humidity levels with the maternal female Our conclusions regarding the occurrence of often covering the eggs completely when the thermogenesis in nest attending female C. humidity levels dropped below 70% (York and rhodostoma should be considered tentative Burghardt, 1988). This behavior was thought to because we only have observations on one regulate moisture level and turgidity of the eggs. individual. Calloselasma rhodostoma may lack We observed slight variation in the extent to sufficient muscle mass to generate appreciable which our female exposed her eggs but exposure heat through shivering. Shivering thermogenesis never exceeded approximately 20%, even during may be restricted to pythons because of their rainfall. Egg exposure was difficult to quantify large size and muscle mass (Shine, 1988). because we could not see the clutch from above. Relative humidity levels at SERS never dropped Costs of nest attendance below 70% nesting. A potential cost of reproduction to female snakes would be an inability to feed during Thermogenesis ovogenesis and/or incubation (Shine, 1988). Our female’s Tb was slightly (1.5°C) but Gravid and pregnant female reptiles often show a significantly higher than the temperature of an reduction or cessation of feeding relative to non- operative temperature model in a nearby, similar gravid females and males (Shine, 1980; Gregory microhabitat and it is possible that some maternal et al. 1999). This generality appears true for thermogenesis was occurring. The comparison of gravid female C. rhodostoma. None of fifty the nesting female’s Tb with Top probably gravid female C. rhodostoma specimens provides the best test of the hypothesis that collected from throughout Southeast Asia had shivering thermogenesis was occurring because food in their guts and their stomachs and livers the operative temperature model was in the same appeared reduced in size (Daltry et al., 1998a). microhabitat as the parent snake. Tair and Tsub Koch (1991) also reports C. rhodostoma cease to were likely to differ from environmental feed during ovogenesis. Our data concur with temperatures inside the rock crevice due these observations as our snake did not appear to exposure to sunlight and wind not present in the feed while gravid. rock crevice. Though statistically significant, the Our female clearly fed during nest small average difference between Tb and Top is attendance just prior to the hatching of the eggs. not compelling evidence to suggest that our Little data exists regarding feeding during nest female was generating body heat above ambient. attendance but two other accounts exist in the Shivering thermogenesis in egg brooding Python literature indicating that captive, nest attending, spilotes spilotes raised Tb almost 7˚C above female C. rhodostoma left their clutch to feed ambient temperature (Harlow and Grigg, 1984). (Smith, 1915; Gloyd and Conant, 1990). A female Python molurus bivittatus raised Tb an Chanhome et al. (2001) indicated that captive, average of 6.2˚C above ambient while brooding gravid C. rhodostoma do not feed until after HILL III ET AL.– NEST ATTENDANCE BY A FEMALE MALAYAN PIT VIPER 65 oviposition but did not specify whether or not our field crew with Malayan Pit Viper they fed during nest attendance. antivenom. Thanks also go to John Murphy and Our female study animal does not appear to two anonymous reviewers for providing editorial have suffered from lack of nutrition due to comments on this manuscript. reproductive activities as evidenced by growth in both SVL (5.0 cm) and weight (3.8 g) during the LITERATURE CITED radio tracking period which ended only about Angilletta, M.J. and A.R. Krochmal. 2003. The two weeks after the eggs hatched. The growth Thermochron: A truly miniature and inexpensive observed for our gravid female is, however, temperature-logger. Herpetological Review, 34: lower than the average 33.5 g weight increase of 31-32. 4 non-gravid C. rhodostoma from West Malaysia Aubret, F., X. Bonnet, R. Shine, and S. Maumelat. during a similar time period (Daltry et al. 2005. Why do female ball pythons (Python regius) 1998b). coil so tightly around their eggs? Evolutionary Some viviparous female pit vipers exhibit Ecology Research, 7: 743-758. post-parturient parental care (Greene, 2002). Bakken, G.S. 1992. Measurement and application of Little parental care was observed after egg operative and standard operative temperatures in ecology. American Zoologist, 32: 194-216. hatching in this study. Ecdysis of the maternal Bergman, R.A.M. 1961. The anatomy of some female may be associated with egg hatching in Viperidae (III), Ancistrodon rhodostoma. Acta C. rhodostoma. Our study animal shed her skin Morphologica Neerlando-Scandinavica, 4: 212- at approximately the same time as the eggs 230. hatched. Bulian (2003) also observed that a Bulian, J. 2003. Notizen zu einem Gelage von female C. rhodostoma in Surathani, southern Calloselasma rhodostoma (Boie, 1827). Sauria, Thailand began shedding simultaneously with the 25: 17-19. hatching of the eggs. Ecdysis appears to be Chanhome, L. 1998. Delayed fertilization, embryonic associated with various reproductive activities in morphology, and neonatal husbandry in Malayan Pit Viper, Calloselasma rhodostoma. The Snake, other crotalines. (Greene et al., 2002; Hill, 28:96-98. 2003). Chanhome, L., P. Jintakune, H. Wilde, and M.J. Cox. 2001. Venomous snake husbandry in Thailand. Wilderness and Environmental ACKNOWLEDGEMENTS Medicine, 12: 17-23. Daltry, J.C. 1995. The evolutionary biology of the This research was conducted with Malayan pit viper, Calloselasma rhodostoma: a permission from the National Research Council study of the causes of intraspecific variation. of Thailand (Permit Number 26/47). Unpublished Ph.D. Dissertation, University of Methodology for handling of animals in this Aberdeen, United Kingdom. study was approved by the Field Museum of Daltry, J.C., Wüster, W. and R.S. Thorpe. 1998a. Natural History’s Institutional Animal Care and Intraspecific variation in the feeding ecology of the Use Committee (Protocol # FMNH 04-6). crotaline snakes Calloselasma rhodostoma in southeast Asia. Journal of Herpetology, 32: 198- We wish to thank the following people for 205. assistance with this project: Beem, Neung, Daltry, J.C., T. Ross, R.S. Thorpe, W. Wüster. Surachit Waengsothorn, the staff of the Sakaerat 1998b. Evidence that humidity influences snake Environmental Research Station for their kind activity patterns: a field study of the Malayan pit hospitality during the course of this study, viper Calloselasma rhodostoma. Ecography, 21: Pannee Panyatwanaporn and the National 25-34, Research Council of Thailand for Permission to Deuve, J. 1970. Serpents du Laos. Office de la conduct this research in the Kingdom of Recherche Science Tech. Outre Mem., 39: 1-251. Thailand, The Queen Saovabha Memorial Fitch, H.S. 1970. Reproductive cycles in lizards and snakes. University of Kansas Miscellaneous Institute, Thai Red Cross Society for providing 66 NAT. HIST. J. CHULALONGKORN UNIV. 6(2), OCTOBER 2006

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