Tuesday, October 19, 2010

The Sulani Snake Festival

The Times of India is carrying the following story, written by Arnab Ganguly and Suman Mandal describing the snake festival in the village of Sulani.

KOLAGHAT: It's a curious mix of rituals and conservation. At Sulani village in East Midnapore near Kolaghat, around 90 km from Kolkata, this annual fair is unlike any other in rural Bengal. What makes Sulani unique is that hundreds of snakes  caught through the year are released after the fair. Kharish, krait and cobra some of the most dangerous of serpents get a new lease of life at Sulani.

Every year on the day of Ashwin Sankranti this year it was on Monday the four-day fair starts, drawing thousands of villagers. It all began 130 years ago with three friends Jhatunath Patra, Abinash Patra and Ishwar Manna deciding to start a fair along with a puja of the snake goddess, Manasa.

"Legend goes that gunins and ojhas used to worship the snake goddess on this day. Snakebites were very common in these parts. The ojhas and gunins were the ones who used to treat the victims. During the fair, the goddess was worshipped and snakes were made to perform. That tradition has stayed on," said Subodh Patra, a descendant of Jhatunath Patra.

A postal department employee, Subodh is now one of leading figures in the fair and a rescuer of snakes. "We rescue the snakes, look after them throughout the year and then release them. Snakes are a very important part of our environment. Through the fair, we try to educate and inform the people about the different kinds of snakes. Not all snakes are poisonous but people have misconceptions," he explained.

During the year, Subodh and other villagers are on the lookout for poisonous snakes and cases of snakebites in the adjoining villages. The snakes are caught and their fangs taken out (in most of the snakes), they are kept for the rest of year and then released in forests or rivers.

"The defence mechanism of a snake gets largely reduced if the fangs are taken out but it can survive. We will have to find out about the fair," said V K Yadav, conservator of forests (western circle).

"I have heard about the fair. NGOs working in that area have told me about it. But I haven't been there," said Dipak Mitra, renowned herpetologist.

Said Biswajit Bagli of Bandhanberia: "Over the years, a number of snakes have been killed. Gradually, the number is coming down. Once a snake is sighted, the villagers send the information to the haat, and from there it reaches the rescuers. Then the snake is rescued."

Like in the past, the snakes are taken to a local temple believed to have been built in the early 19th century. After a puja, vermillion is applied to the hood of the snakes and they are taken to the nearby high school ground. On two makeshift platforms, Patra and his followers hold the snakes for the public to see.

"We have been visiting the fair since our childhood. The number of snakes that are displayed has increased over the years. Also, the number of snakes being killed has come down," said Swadesh Patra of Pratimchak.

Sunday, October 17, 2010

A Rare Death From A US Rattlesnake Bite

San Diego’s East County Magazine (October 16, 2010) – is reporting that a 67-year old fly fisherman from La Jolla stopped breathing minutes after being bitten by a rattlesnake while wading across a stream near Cuyamaca Reservoir. William “Skip” Price was conducting a Steelhead Trout survey with four other volunteers when he stepped on the snake and was bitten on the foot. He was wearing water sandals, not waders or boots, which could have prevented the deadly injury. Gary Strawn of Santee, conservation chairman of San Diego Fly Fishers, told the Union-Tribune that Price stopped breathing within minutes, and that Strawn and other performed CPR for about 20 minutes until paramedics arrived. A Sheriff’s helicopter air lifted the victim to Palomar medical Center in Escondido, where he was declared dead at 1 p.m. today. Strawn never saw the snake, but concluded it must have been a large one because the bite marks on Price’s foot were an inch and a half across.Emergency guidelines urge snakebite victims to seek immediate medical care—an option not readily available in backcountry areas. But most medical experts have long said that rattlesnake victims who receive medical treatment within the first hour are likely to survive. Price’s rapid death highlights concerns raised by a UCSD toxicologist, who believes rattlesnake venoms locally have evolved to become more toxic than in the past. “The venom from rattlesnake bites in San Diego County is becoming more potent, causing an extreme reaction in patients, toxicologists at the University of California, San Diego Medical Center reported,” according to a June 2008 10 News article which said USCD toxicologists had reported unusually powerful snakebites for the second year in a row. Bites, often from the Southern Pacific rattlesnake, had led to severe weakness, trouble breathing and low blood pressure among patients. Within minutes, the victim can get lightheaded, collapse and go into shock, according to the report.

Dr. Richard Clark, director of medical toxicology at UCSD and head of the local division of the California Poison Control System, told 10 News in that interview that the reason for the increasing toxicity was unknown. "Some speculate that with the modern world encroaching on nature, it could be survival of the fittest," he said. "Perhaps only the strongest survive." A 2010 interview with Clark confirmed that the number of serious reactions has remained higher than in the past. UCSD is working to develop more powerful anti-venom. But such treatments can work only if patients receive medical treatment promptly—a feat that is not always possible in remote areas of East County. With San Diego's warm climate, snakes can be a year-round hazard.  Never hike through brush or water where you can't see what you're walking on.  On the trail, wear hiking boots and jeans.  Avoid reaching up onto rocks or boulders, favorite places for rattlesnakes to sun themselves, and never reach into rocky crevasses or brush.  If you hike with your dog, keep the dog on a leash and on the trail with you at all times.  If you hear a tell-tale rattle, freeze, locate the snake, and back slowly away. While bites to the head, neck or torso are considered the most dangerous, as Price's case shows, even bites to the extremities can be fatal.  Carry a cell phone when hiking to call for help if needed, and always seek prompt medical attention if bitten.

High Latitude Garter Snakes

The post on Garter Snakes in Newfoundland attracted much attention, so I investigated high latitude garter snakes a bit further. As far as I can see this news report is the first evidence of snakes from Newfoundland. But, in central and western Canada garter snakes have been known to reach relatively high latitudes, latitudes, higher than that report in Newfoundland.

Garter Snakes are quite cold tolerant and range farther north than any other North American snakes. They are also capable of submerged hibernation, a poorly studied behavior (Murphy 2010) and one that undoubtedly increases their survival at high latitudes.

John Richardson (1851) [in Bauer and Russell, 2001] appears to be the first to report garter snakes in central Saskatchewan, when he observed garter snakes at Serpent Lake. The earliest reference to garter snakes in Alberta appears to be Ǽmilius Simpson’s journal written in 1826. He was traveling on the North Saskatchewan River and passed the confluence with the Stone River at noon, he was at 53º45’34”N, 110º40’W and the temperature was 75ºF. The bank was limestone and clay, and he wrote, “…we passed great numbers of small striped Black & green snake swimming from the South to the North Bank of the River & strewed along the Sandy Beach on the North Shore, as if enjoying the powerful influence of the Sun, & it appeared that those crossing were leaving the cold of the Northern aspect to gain the more pleasing heat of the southern exposure.”

Bauer and Russell (2001) examined Simpson’s account and adjusted his co-ordinates, suggesting that they were actually, 53°45’15”N, 111°10’W and the area Simpson passed at noon is now known as Fort Island. Three species of garter snakes occur in Alberta: the Plains Garter Snake, Thamnophis radix, the Wandering Garter Snake, T elegans, and Red-sided Garter Snake, T sirtalis. The Wandering Garter Snake is restricted to the southwestern Albert in the Rocky Mountain and prairie biomes, but specimens are occasionally found much further north, and the species is often associated with rivers. All modern records from the vicinity of Fort Island are attributable to T radix, and most are from localities in Aspen Parkland or Prairie, with a few Plains Garter Snakes collected in the Boreal Forest Biome north of the North Saskatchewan River. Simpson’s color description describes both the Red-sided Garter Snake and the Plains Garter Snake and both species are associated with water and swimming behavior, T. sirtalis more so.

Larsen et al. (1993) studied this snake at Wood Buffalo National Park (59º49'N, 112º W) in the Northwest Territories, Canada. This is the highest known latitude for Thamnophis sirtalis. Thet found females rarely gave birth in 2 successive years. Female snakes matured at larger body sizes (570 mm) than snakes in Manitoba (527 mm), and they had smaller litter sizes than Manitoba females. The authors conclude that there is no single suite of life history traits for northern populations of garter snakes. The smallest gravid female they observed was 670 mm, but found a 570 mm female that had mated.

But are there garter snakes in Alaska? McDonald (2003) noted that the valleys of the Stikine River and Taku River (and perhaps Unuk River) could potentially allow Thamnophis access to the coast from the interior British Columbia, however, it remains unclear if snakes occur in these drainages. A preliminary search for garter snake records from major drainages that flow into coastal Alaska did not produce any evidence of their presence. McDonald reports that a resident of Telegraph Creek, BC, stated that he could not recall anyone ever seeing a snake in the area. The Common Garter Snake (Thamnophis sirtalis) has been reported north of Terrace, British Columbia, in the watersheds of the Nass and Skeena rivers, and along the eastern side of the province as far north as the Peace River District (Gregory and Campbell 1984). The Western Terrestrial Garter Snake (T. elegans) is found along the British Columbia coast, including Vancouver Island, as far north as the Skeena River Basin, and east of the Rockies as far north as the Peace River District (Gregory and Campbell 1984).

In eastern Canada the Maritime Garter Snake, Thamnophis sirtalis pallidulus, covers a considerable amount of geography. Bleakney (1959) redescribed the subspecies Thamnophis sirtalis pallidulus noting that its coloration was distinct over a large area and that it shows sexual dimorphism in ventral scale and subcaudal counts, commenting that T. s. pallidulus from Nova Scotia have 6 to 7 fewer ventral scales and 7 to 10 fewer subcaudal scales than T. s. sirtalis. And, he writes, “The subspecies [T. s. pallidulus] ranges throughout the Atlantic Provinces (exclusive of Newfoundland), westward into New Hampshire and thence northwestward to James Bay, and eastward again along the north shore of the Gulf of St. Lawerence.”

Barnes et al. (2006) examined the ecology and morphology of the population of the Maritime Garter Snake on Georges Island, Nova Scotia and marked 391 garter snakes, reported a male to female ratio of 0.8:1.0; and a population density for adult snakes of 120/ha. They found these snakes to be exceptionally docile, and the population contained melanistic individuals. Perhaps most remarkable they found female snakes reproductively active at a body length of 350 mm. This is quite small, Fitch (1965) reported that Kansas males mature at about 400 mm, and females mature at about 500 mm or 15 months of age. It seems likely that high latitude populations will grow more slowly and mature at smaller sizes and older ages due to abbreviated season of activity, but the studies done to date show a range of sizes at maturity for female snakes.

Gregory and Larsen (1993) studied geographic variation in litter size and neonate size in several populations of garter snakes (T. sirtalis) across Canada and found gravid females differed significantly in body size between the sites. Even after they corrected for inter-site differences in female body size, there were highly significant differences in litter size and neonate size. Populations with large litters tended to have small progeny, but they found only weak evidence of a "tradeoff" between neonate size and litter size within populations. Snakes from eastern Canada were relatively small at maturity and produced large litters of very small young, while those from western Canada were usually large and produced smaller litters (for a given body size) of larger young. 

 The map above shows the Newfoundland Record (red Triangle), the Wood Buffalo population (grey square), the approximate range of T. s. pallidulus (blue shading) and some high latitude locations for sirtalis on the west coast (black spheres).  

This is not an exhaustive compilation of high latitude Thamnophis. If you know of others leave a comment.

Barnes, S. M., C. M. Dubesky, and T. B. Herman. 2006. Ecology and morphology of Thamnophis sirtalis pallidulus (Maritime Garter Snakes) on Georges Island, Nova Scotia. Northeastern Naturalist 13(1):73-82.

Bauer, A. M. and A. P. Russell.  The First Record of Reptiles in Alberta: AEmilius Simpson's Journal of 1826 Herpetological Review 32(3):174-176

Bleakney, S. 1959. Thamnophis sirtalis sirtalis (Linnaeus) in eastern Canada, redescription of T. s. pallidula Allen. Copeia 1959(1):52-55.

Fitch, H. S. 1965. An ecological study of the garter snake, Thamnophis sirtalis. University of Kansas Publication, Museum of Natural History 15:493-564.

Gregory, P. and K. W. Larsen. 1993. Geographic variation in reproductive characters among Canadian populations of the common garter snake (Thamnophis sirtalis). Copeia 1993(4):946-958.

Larsen, K. W., P. T. Gregory, and R. Antoniak. 1993. Reproductive ecology of the common garter snake Thamnophis sirtalis at the Northern Limit of its range. American Midland Naturalist 129:336-345.

McDonald, S. O. 2003. Amphibians and Reptiles of Alaska, A Field Handbook. http://www.alaskaherps.info/

Murphy, J. C. 2010. Secrets of the Snake Charmer, Snakes in the 21st Century. Bloomington: iUniverse. 420 pages.

Friday, October 15, 2010

Humidity Improves the Gecko's Grip

The Journal of Experimental Biology  http://jeb.biologists.org is reporting this morning that the ability of gecko toes to grip surfaces is impacted by water. Gecko toe pads are covered with rows of fine, hair-like filaments called setae. Michael Prowse examined the material properties of the lizard’s feet, knowing that the setae are composed of keratin and keratin is softened by high humidity. Repeatedly stretching and releasing a strip of setae at three different rates (0.5, 5 and 10 Hz) in environments ranging from 10% to 80% humidity, allowed the researchers to measure the force transmitted through the strip to calculate the strip's elastic modulus – how much elastic energy is stored – to see how it changed. As the humidity rose, the elastic modulus decreased by 75% and the strip of setae became softer. So the strip of setae became more deformable as the humidity rose, but could the increased softness explain the gecko's improved attachment under damp conditions?
Puthoff built a mathematical model to see if softer, more deformable, setae could explain the gecko's improved attachment at high humidity and found that it did. Not only did increased softness strengthen the contact between the setae and the surface but also it made it easier for the reptile to peel its foot off. So instead of improving gecko's attachment through microscopic bridges, higher humidity softens the setae that coat the gecko's feet to help them hold fast and peel free with ease.
In 2002, Kellar Autumn found that these dry hairs are in such intimate contact with surfaces that geckos 'glue' themselves to surfaces using van der Waals forces and do not use fluid adhesives. More recently it was suggested that geckos might benefit from additional adhesion in humid environments through capillary action provided by microscopic.

While this study has implications for material research, it may also suggest a reason why some geckos have the habitat preferences and distributions they do.

Citation: Puthoff, J. B., Prowse, M. S., Wilkinson, M. and Autumn, K. (2010). Changes in materials properties explain the effects of humidity on gecko adhesion. Journal of Experimental Biology. 213: 3699-3704.

Thursday, October 14, 2010

Western Cottonmouth Survival Rates and Use of Space

Cottonmouths have always been of interest because they are the only pit viper that has been able to exploit aquatic environments. Why this is so, is a puzzle. Look at virtually all other lineages of snakes and you find they almost always contain species, or groups of species, that have adapted to water. The most prominent exceptions are the scolecophidians (blind snakes, threadsnakes and dawn snakes) and the vipers. The scolecophidians may be so specialized for burrowing and eating social insects that invading aquatic habitats is not an option for them. But why the vipers have not invaded the water is more obscure. Only the cottonmouth exploits aquatic resources and seems to spend a substantial amount of time in the water, but even it quite terrestrial and not completely adapted to water. Populations that hibernate do so in terrestrial situations, the snakes often thermoregulate out of the water, and they use a variety of terrestrial habitats, albeit usually near water. Two recent papers reveal parts of its life history. Rose et al.(2010a) estimate the survival of the western cottonmouth (Agkistrodon piscivorus leucostoma) in central Texas using the Cormack-Jolly-Seber Model that accounts for delectability. They studied the annual probability of survival of the western cottonmouths at Honey Creek, Comal County, Texas for 11 years. Honey Creek is a spring-fed stream flowing into the Guadalupe River. Cottonmouths can be secretive have a low probability of detection (0.12) and the study produced relatively small sample (n = 51). However, the estimate of survival was reasonably precise (coefficient of variation was 4%). The study time included multiple floods and droughts, and therefore, represents a relatively wide range of conditions to which western cottonmouths are exposed at this locality. The results suggested adult snakes have a 0.81 probability of survival in any given year, an annual survival rate similar to that reported for other pit vipers. In a second paper, Rose et al. (2010b) looked at the Honey Creek cottonmouth population to see how it used space along the stream. They made 57 searches along a 1564 m study site and marked 39 mature snakes, 14 subadult snakes, and 4 juveniles. Recapture frequency did not differ between sexes, but females outnumbered males (2.3:1) and adults were recaptured more frequently than juveniles. Distances between captures were less than predicted if distributions were random, and distances did not vary with number of times captured or time between captures. Most snakes were sedentary, but a few individuals made long distant movements. At least some the snakes were displaced by flooding but returned after the water subsided.

A Western Cottonmouth from Johnson Co., Il. JCM
Rose, F. L., T. R. Simpson, J. R. Ott, R. W. Manning, and J. Martin. 2010a. Survival of Western Cottonmouths (Agkistrodon piscivorus leucostoma) in A Pulsing Environment. The Southwestern Naturalist 55:11-15.

Rose, F. L., T. R. Simpson, J. R. Ott, and R.W. Manning. 2010b. Use of Space by Western Cottonmouths (Agkistrodon piscivorus) Inhabiting a Variable–Flow Stream. The Southwestern Naturalist 55(2):160-166.

Wednesday, October 13, 2010

Temperature and the Placticity of Neonate Snakes

Australian Tiger Snakes, Notechis scutatus. JCM
In thinking about the impact of the global warming and the evapotranspiration rate on reptiles I did some Internet searching and found an article published earlier this year that experimentally examined how snakes would respond to temperature shifts after they were raised under different thermal conditions as neonates. Aubret and Shine (2010) used captive born Australian Tiger Snakes, Notechis scutatus, (Family Elapidae) to see how snakes respond to temperature changes. Forty-three Tiger Snakes were raised in cold (19-22C), intermediate (19-26C) and hot (19-37C) thermal gradients. The snakes adjusted their thermal behavior so that when they were tested 14 months later their body temperature, speed of movement, and anti-predator behavior did not differ between the groups - the snakes had modified their behaviors to compensate for the different temperature regimes under which they were raised in. However, when the temperatures the snakes were kept at were changed to follow year to year variations, the snakes failed to adjust their behaviors. Snakes raised at cool temperatures and then shifted to hot temperatures showed a higher mean body temperature for at least two months after they were exposed to the new thermal conditions. This suggests that the temperatures snakes experienced when young impact their thermal behavior later in life. So, the young snakes proved to be quite flexible in their ability to adapt to the temperature regimes they were exposed to. But, as they aged, they continued to use the same thermal regulatory behaviors when placed into new thermal environments, even though those behaviors were inappropriate for their current thermal environment. Aubret and Shine suggest the mean body temperature depends more on the individual snake's early experience than on the thermal opportunities present at a given point in time. And, that the challenge of adapting to global warming is not the shift in the mean values but the increases in annual variations in temperatures. As the previous post suggests large areas of the Southern Hemisphere are drying and changes in the vegetation and fauna can be expected. Ultimately this trend will result in extinctions and produce a greatly reduced biodiversity.

Aubret, F. and R. Shine. 2010. Thermal plasticity in young snakes: how will climate change affect the thermoregulatory tactics of ectotherms? The Journal of Experimental Biology 213:242-248.

Monday, October 11, 2010

This Can’t Be Good: Squamate Diversity and the Evapotranspiration Rate

The following is a composite of the articles listed at the bottom of the post. As well as a press release from Oregon State University about the Jung et al. study and carried by Eureka Alert.

Earlier this year David Bickford and colleagues summarized the impact of climate change on the herpetofauna of Southeast Asia. They predicted the following impacts as the temperature increases: desiccation of frog eggs laid in leaf litter and soil; changes in tadpole behavior due to low dissolved oxygen followed by an increase in tadpole mortality; an increase in susceptibility to diseases; loss of freshwater turtle habitat; a decrease in mass or population size due to increased metabolism; skewed sex rations in TSD species; elimination of males or females in TSD species and more species of reptiles showing single sex populations; reduced population size of fossorial species because of soil desiccation; loss of marine turtle prey base and subsequent population declines; and reduced diversity at low and high elevations; all of these alterations increase competition and changes in community composition.

Additionally, Christy McCain (2010) used 25 elevational gradients of reptile diversity from temperate, tropical and desert mountains in both hemispheres that spanned the latitudes from 10.3° N to 46.1° N. She found reptile richness and, specifically snake, as well as lizard, richness on mountains showed four distinct patterns: decreasing, low-elevation plateaus, low-elevation plateaus with mid-elevation peaks, and mid-elevation peaks. Reptile richness at various elevations was most strongly correlated with temperature. The temperature effect was mediated by precipitation; reptile richness was more strongly tied to temperature on wet gradients than on arid gradients. Area was secondarily important, while the mid-domain effect was not strongly associated with reptile diversity on mountains. Montane reptile diversity patterns did not follow the predicted temperature–water effect, as all diversity patterns were found on both wet and dry mountains. However, precipitation’s effect on temperature most likely reflects reptiles using basking opportunities that are more abundant on arid mountains than wet mountains because of lower humidity, sparser vegetation and less cloud cover at low and intermediate elevations.
Now, a study lead by Martin Jung from the Max Planck Institute for Biogeochemistry in Germany report that the soils in large areas of the Southern Hemisphere, including major portions of Australia, Africa and South America, have been drying up for the past decade. This is the first major study to examine evapotranspiration on a global basis.

Most climate models have suggested that evapotranspiration (the movement of water from the land to the atmosphere) would increase with global warming. Jung et al’s study published online this week in the journal Nature, found that's exactly what happened from 1982 to the late 1990s.

However, in 1998, this significant increase in evapotranspiration – which had been seven millimeters per year – slowed dramatically or stopped. In large portions of the world, soils are now becoming drier than they used to be, releasing less water and offsetting some moisture increases elsewhere.

Due to the limited number of decades for which data are available, scientists say they can't be sure whether this is a natural variability or part of a longer-lasting global change. But one possibility is that on a global level, a limit to the acceleration of the hydrological cycle on land has already been reached.

Jung et al suggest the trend could reduced terrestrial vegetation growth, reduce carbon absorption, and reduce the natural cooling mechanism created by evapotranspiration. The results would produce increased heating of the land’s surface, more intense heat waves, and a feedback loop that could intensify global warming.

Regions that show most severe drying include southeast Africa, much of Australia, central India, large parts of South America, and some of Indonesia. Most of these regions are historically dry, but some are actually tropical rain forests.

The rather abrupt change from increased global evapotranspiration to a near halt in this process coincided with a major El Nino event in 1998, the researchers note in their report, but they are not suggesting that is a causative mechanism for a phenomenon that has been going on for more than a decade now.
Greater evapotranspiration was expected with global warming, because of increased evaporation of water from the ocean and more precipitation overall. And data indeed show that some areas are wetter than they used to be. However, other huge areas are now drying out. This could lead to increased drought stress on vegetation and less overall productivity. The result could be less carbon absorbed, less cooling through evapotranspiration, and more frequent or extreme heat waves.

Evapotranspiration returns about 60 percent of annual precipitation back to the atmosphere, in the process using more than half of the solar energy absorbed by land surfaces. This is a key component of the global climate system, linking the cycling of water with energy and carbon cycles. Long term studies will be needed to determine if these changes are part of decade trend or a longer-term shift in global climate, the researchers said.

While changes in the evapotranspiration rate are likely to favor some species of squamates at some localities, others will be negatively impacted, thus radical changes in the species composition of communities seems likely.

Bickford, D., S, D. Howard, J. J. Ng, and J. A. Sheridan. 2010. Impacts of climate change on the amphibians and reptiles of Southeast Asia. Biodiversity and Conservation 9:1043-1062.
McCain, C. M. 2010. Global analysis of reptile elevational diversity. Global Ecology and Biogeography 19:541-553.

Jung, M., M. Reichstein, P. Ciais, S.I. Seneviratne, J. Sheffield, M.L. Goulden, G. Bonan, A. Cescatti, J. Chen, R. de Jeu, A.J. Dolman, W. Eugster, D. Gerten, D. Gianelle, N. Gobron, J. Heinke, J. Kimball, B.E. Law, L. Montagnani, Q. Mu, B. Mueller, K. Oleson, D. Papale, A.D. Richardson, O. Roupsard, S.W. Running, E. Tomelleri, N. Viovy, U. Weber, C. Williams, E. Wood, S. Zaehle, K. Zhang. 2010. A recent decline in the global land evapotranspiration trend due to limited moisture supply. Nature xxxx: xxx-xxx. DOI 10.1038/nature09396.

How Do Snakes Know When to Stop Feeding?

Feeding strategies in snakes have yet to be fully investigated. Feeding frequency is one of the more poorly understood aspects. While field studies suggest snakes ambush, actively search, or use a combination of both hunting strategies, little is known about the motivation for hunting behavior. A few studies on vipers suggest snakes may feed as few as five or six times per year. This however, cannot be applied to all snakes, particularly those species that consume numerous small prey items, such as the social insect-eating threadsnakes and blindsnakes, the earthworm-eating uropeltids, the small fish-eating homalopsids, and the fish egg-eating sea snakes. These species must feed much more frequently. Boas and pythons are well known for eating relatively few large prey and capable of fasting for long periods of time (as long as 36 months). One aspect of feeding is satiety, it has been studied extensively in other groups of vertebrates but it is poorly understood in reptiles. Torben P Nielsen and colleagues have now investigate time-dependent satiation in two species of constricting snakes the Ball Pythons (Python regius) and Yellow Anaconda (Eunectes notaeus). They show that satiation depends on both fasting time and prey size and they define satiation as the state achieved when a snake would not voluntarily consume a second prey presented to it Ball Pythons fed with mice of a relative small prey mass (the mice were 15% of the snake’s mass), satiety response occurred 6 to 12 hours after feeding, but 24 hours after feeding the pythons regained their appetite. When the pythons were give mice that were 10% of their body mass the snakes feed continually during the experiment. The Yellow Anacondas did not show the satiety response until they had been fed prey that was 20% of their mass, and the response develop between 6 to 12 hours after feeding, but it was statistically not significant. The anacondas remained satiated for 24 hours. Handling time (from strike until prey swallowed) increased with the prey’s body mass and handling time decrease between the first and the second prey, there was also a positive correlation between handling time and the mass of the snake.

Nielsen T. P., M. W. Jacobson, T. Wang 2010. Satiety and eating patterns in two species of constricting snakes. Physiology and Behavior. 2010 DOI: 10.1016/j.physbeh.2010.09.001