ThesisPDF Available

Population ecology of the dog-faced water snake Cerberus rynchops at Sungei Buloh Wetland Reserve, Singapore.

Authors:
A preview of the PDF is not available
... Prey species that could not be positively identified in the field were photographed at high magnification and sent to a colleague (Lim, KKP pers comm.) for identification. In our review of life history studies of piscivorous species, we were able to obtain dietary data of three other focal organisms, namely the smooth-coated otter (Theng 2011), the Malayan water monitor (Abdur Rashid 2004 ) and the dogfaced water snake (Chim 2009), from which we extracted specific records. All three studies were carried out at the Sungei Buloh Wetland Reserve (1.4467°N, 103.7302°E). ...
... Four species of cichlids were reliably identified from the diet of the smooth-coated otter, the highest dietary diversity of alien species among the four predators compared although the spraint remains did not allow species-level identification for many prey items (Theng 2009). (2000) as one of the worst 100 invasive species globally 2 Likely to occur as newly released individuals, and is not known to be established (see Ng et al. 1993) Of 15 prey identified to species level in the diet of the dog-faced water snake (Chim 2009), six were alien, of which three were cichlids. A common species of estuarine streams and drainage canals (Ng and Tan 2010), the alien Mexican molly (Poecilia sphenops) was one of two dominant prey items for that species based on total biomass, the other which is the native Javanese ricefish (Oryzias javanicus) (Chim 2009) while cichlids only formed a small proportion of its diet. ...
... (2000) as one of the worst 100 invasive species globally 2 Likely to occur as newly released individuals, and is not known to be established (see Ng et al. 1993) Of 15 prey identified to species level in the diet of the dog-faced water snake (Chim 2009), six were alien, of which three were cichlids. A common species of estuarine streams and drainage canals (Ng and Tan 2010), the alien Mexican molly (Poecilia sphenops) was one of two dominant prey items for that species based on total biomass, the other which is the native Javanese ricefish (Oryzias javanicus) (Chim 2009) while cichlids only formed a small proportion of its diet. Three species of alien reptiles (families Agamidae, Emydidae, Trionychidae) and one amphibian (family Ranidae) were identified in the diets of the four predators. ...
Article
Full-text available
We report for the first time the diversity of known aquatic alien species in the diets of four piscivorous predators in Singapore through a review of published and unpublished studies, and our empirical data. Of 15 aliens identified to the species level, 11 were fish, including the highly invasive tilapia (Oreochromis mossambicus [Peters, 1852]). Other alien species include the abundant red-eared slider (Trachemys scripta elegans [Wied-Neuweid, 1839]) and the American bullfrog (Lithobates catesbeiana [Shaw, 1802]). We hypothesize that the diversity of established alien species in Singapore's aquatic habitats allows for novel ecological interactions, one of which is predation by native species. Our study provides preliminary evidence that alien and invasive species may benefit some native piscivores as a source of prey although it is not possible to infer relative composition of these alien species given our limited data. Future studies should investigate the ecological dynamics of these interactions, including the relative importance of these alien prey to diets and survival of predators.
... Four of these species are from the family Homalopsidae, restricted to muddy substrate and estuaries, exhibit a wide range of diets (Voris and Murphy 2002). Cerberus schneiderii is a generalist feeding on fishes and crustaceans (Chim 2009). The other three species are crustacean specialists, usually associate with mud lobster mounds that serve as refuge areas for their prey (Karns et al. 2002). ...
Book
Full-text available
he Singapore Blue Plan 2018 (hereafter ‘The Blue Plan’) is a proposal for the conservation of marine ecosystems, prepared by members of Singapore society, and submitted to the Government for consideration. It was initiated by marine biologists with academics, volunteers, stakeholders, and concerned citizens. The Blue Plan synthesizes the current state of knowledge for marine environments, reviews relevant legislature and advocates comprehensive sustainable methods to manage this important ecosystem
... Many accounts demonstrate that a species not normally inclined to sidewind will do so when placed on sand, or on a very smooth artificial surface, such as linoleum (e.g., Mosauer 1930;Gray 1946;Gasc 1974;Jayne 1986Jayne , 1988Klauber 1997;Scanlon 2001;details in Supplementary Table S3). Some species sidewind on mud, which may present some of the same challenges as sand due to its granular nature (although wet granular materials behave differently from dry granular materials, so mud likely also differs from sand in interesting ways) (Wall 1919;Bustard 1969;Jayne 1986;Jayne et al. 1988Jayne et al. , 1995Chim 2009; details in Supplementary Table S2). Even among desert species that regularly sidewind in nature, some of them will use sidewinding on sand but switch to other types of locomotion when placed on crushed aggregate (e.g., Echis spp. ...
Article
Full-text available
Specialist species often possess adaptations that strongly distinguish them from their relatives, obscuring the transitional steps leading to specialization. Sidewinding snakes represent an example of locomotor specialization in an elongate, limbless terrestrial vertebrate. We typically think of sidewinding as a gait that only a handful of very specialized snake species perform, mostly vipers from sandy desert environments. Some of these desert-dwelling vipers are so specialized that they only rarely use more common types of locomotion. However, some non-viper species sidewind facultatively in particular circumstances, and a few may regularly sidewind under natural conditions. Numerous accounts report facultative sidewinding in species that more typically perform other types of locomotion. I have compiled these accounts, uncovering evidence that dozens of species perform sidewinding with varying proficiency under a variety of conditions. These facultative sidewinders can reveal insight into the evolution and biomechanics of sidewinding, and they provide ample opportunities for future study.
Article
Full-text available
Snakes of the genus Cerberus Cuvier, 1829 occupy a unique, widespread coastal distribution and have a salt-tolerant physiology that allows members of the genus to move across a wide range of salinities from full salt water to freshwater. Cerberus nomenclature is revised based upon morphology and builds on previous molecular studies. Three species have been recognized by recent workers, here we recognize five species: the South Asian C. rynchops (Schneider 1799); the Southeast Asian-Philippine C. schneiderii (Schlegel 1837), a new combination; the freshwater Philippine endemic C. microlepis Boulenger 1896; the Australopapuan C. australis (Gray 1842); and a new species from Micronesia. We also select a lectotype for Homalopsis schneiderii Schlegel based upon a figure published in 1837 and restrict the type locality for this species to Timor. Evidence is also presented for a population of Cerberus australis in Indonesia, west of Weber's Line.
Article
Full-text available
Based on a collection from the Muar River estuary in western peninsular Malaysia, we quantified the morphology, reproductive effort and diet of the previously rare homalopsine snake Bitia hydroides. The dentition of B. hydroides is unusual because of enlarged anterior palatine teeth which have lengths that exceed those of all other teeth, including the posterior maxillary fangs. Enlarged palatine teeth have only been described previously for a single species of snake. Despite this unusual dentition, B. hydroides fed on oxydercine and bottom-dwelling species of gobies, which are consumed by sympatric species of marine snakes. Females were considerably larger than males. Reproduction was strongly seasonal and out of phase with that of the sympatric species of hydrophiids, and the size distribution of the snakes suggested that the age of first reproduction approximates one year. For 13 females, litter size ranged from 1-10 (x̄ = 4.2) and was significantly correlated with maternal size. Relative clutch mass ranged from 0.07-0.35 (x̄ = 0.22) and was not correlated with maternal size.
Article
Full-text available
I studied the ecology of a discrete population of Graham's crayfish snake (Regina grahami) in northwestern Missouri continuously from 1979-1983. As is true of other natricines, females were significantly longer and heavier than males. Snakes were active from April through early November, with peaks of activity in early spring and late autumn. Regina in this population were mainly diurnal; nocturnal activity was confined primarily to summer months. In comparison with R. grahami from Missouri, snakes in Louisiana began and ended their activity season much earlier and had a unimodal activity pattern. Females in Missouri produced a single brood each year, with a mean brood size of 11.6 (range = 5-16). Larger females produced larger broods. The sex ratio of offspring was skewed in favor of females, and there was evidence of sexual size dimorphism among neonates, with males larger than females in body length but not body mass. All prey items were molting crawfish; feeding frequency was highest among juveniles. Except for sexual dimorphism in offspring size and a biased sex ratio at birth, few major ecological differences were found between R. grahami and other natricine snakes.
Article
Full-text available
Describes aspects of population densities, activity and reproduction. The species is strictly nocturnal, moonlight having a depressive effect on activity. In daytime, the snakes are confined to shoreline shallows, lying beneath stones, raising their heads to the water surface for air. Food is entirely of Cichlidae. -P.J.Jarvis
Article
Near the mouth of the Muar River, 69% of prey items were the goby Oxuderces dentatus, but as C. rynchops become larger, ariid catfish, mullet and taenioid gobies are increasingly important portions of the diet. C. rynchops usually forage on or near the bottom or in very shallow water. No evidence of a seasonal reproductive pattern was found. -from Authors
Article
A five-year mark-recapture study at Sella Nevea, a montane (1100 m a.s.1.) site in the Carnic Alps, provided information on diets, growth rates, and reproductive output in an Italian population of the wide-ranging grass snake, Natrix natrix. Our snakes resembled a previously-studied population in lowland Sweden in terms of body size at sexual maturation in females (70 cm) and mean adult female body length (82 cm). However, growth rates were lower in our population, and sexual maturation was delayed (6–8 years, versus 4–5 years in Sweden), perhaps because of the cool climate and relatively brief growing period each year. Females produced a single clutch of 4–24 eggs in late July each year. Larger females produced larger clutches, but clutch size relative to maternal size was lower than in Swedish grass snakes. Hatchling sizes and Relative Clutch Masses (RCMs) did not shift with increasing female size. RCMs may provide a useful index of ‘costs of reproduction’ in this population, because females with high RCMs were very emaciated after oviposition, and hence may experience a greater risk of mortality, as well as a high energy expenditure. Prolonged incubation gave rise to longer, thinner hatchlings, but the low environmental temperatures at the study site may favour early hatching (and hence, result in a shorter fatter hatchling emerging from the egg, with more of its energy stores unused). Compared to sympatric viviparous snakes (Coronella austriaca and Vipera berus), the oviparous grass snakes can achieve a much higher reproductive output owing to a larger clutch size and more frequent reproduction (annual, rather than biennial or triennial). The abundant prey resource used by grass snakes (amphibians) may also enable them to recoup energy more rapidly after reproduction; dietary composition shifts ontogenetically in both sexes, with the largest prey (mice and adult toads) taken primarily by large female snakes.
Article
Data sets on the reproductive biology of the western ribbon snake, Thamnophis proximus, in general, emphasize either characteristics related to the females or to the offspring but not both. In addition, records from multiple years at a given locality are rare. Gravid female T. proximus were collected for three consecutive years (1999-2001) from a bottomland hardwood site in northeastern Texas. These females were kept in captivity for a short time until they gave birth. Data recorded included maternal snout-vent length (SVL), pre-parturient mass, postparturient mass, clutch size, offspring SVL, offspring total length (TL) and offspring mass. In addition, mean clutch size and mean relative clutch mass were calculated for each year. Clutch mass and clutch size were both correlated with female SVL for the 10 clutches obtained in 2001. There were differences in parturition dates, clutch mass, female size and offspring size among the snakes in the three different years as well as differences between these records and previous reports. Thus both geographic variation and temporal differences are evident in the reproductive traits of this species of snake.
Article
Over a 15-year period, 359 black rat snakes were captured, mostly on a 750-acre area; because many were recaptured after marking, records totaled 516. The average emergence date was 16 April and 27 October was the average date for the end of the season's activity. Calculated home ranges averaged 29 acres for males and 23 acres for females. Males are more inclined to wander, but in both sexes the tendency to remain within a familiar range is strong. Hatchlings appear in late summer or early autumn and range in snout-vent length from 290 to 368 millimeters; typical one-year-olds range from 500 to 650 millimeters. Sexual maturity is attained in the fourth year usually at a snout-vent length of a little less than 900 millimeters in males (which usually mature somewhat earlier) and a little more than 900 millimeters in females. Monthly gains in the growing season average 36 millimeters in the young of each sex. In the third or fourth year there is abrupt slowing, most marked in the females. Large adult males gain on the average a little more than three millimeters per month in the growing season. On the basis of observed growth rates more than one-fourth of the rat snakes recorded were eight years old or older, and some may have been more than 20 years old. The rat snake depends primarily on small birds and mammals for food, but takes an occasional frog, lizard, or snake. Birds are preyed upon chiefly in the nesting season; few adults are eaten. The red-tailed hawk is an important natural enemy; 577 instances of predation on rat snakes were recorded for this kind of hawk, but for other predators few records were obtained.