Saturday, July 25, 2009

The Diamondback Rattlesnake’s Predatory Might

A new project at work has kept me in the field for the last couple of weeks and has severely dimensioned my time available for blogging; I should be freed up by the middle of next week and be able to get Ecographica back in gear then…

On the positive side of things, the abundance of recent fieldwork has resulted in several encounters with nature, and a slow starting Saturday has provided the opportunity to share one such wildlife sighting. However, before proceeding a warning must be forwarded; if you are lucky enough to stumble onto one of these herps in the wild, ensure that you’re stumbling is undertaken with the utmost caution – or your luck may run out very quickly! Although the below video and picture appear to be taken at close range, they in fact have been recorded at a distance and later edited from the safety of a desk.

Getting on with the tale (or, in this instance “tail”), while trudging through a chunk of palmetto flatwoods in north central Florida last week, a break in the radiating palmetto leaves underfoot caught my eye – a diamondback rattlesnake! And a big one at that!

Photo was taken by Charlie, a fellow ecologist that happens to be a little faster at drawing his camera.

The eastern diamondback rattlesnake Crotalus adamanteus is the largest pitviper in the Western Hemisphere and can achieve sizes (length) of more than seven feet. Fairly common here in Florida, their range extends north along the Atlantic seaboard to the Carolinas and westward to about New Orleans, Louisiana. They do well in habitats such as palmetto flatwoods due to the ample cover provided by the palmetto leaves (“palmetto” = Seronoa repens).

The leaves provide shade for regulating body temperatures, conceal them from fumbling ecologists, and offer excellent camouflage for setting ambushes – and setting ambushes is what they do best. They lay in wait for hours, motionless; then, when the radiating heat of an approaching rabbit, bird or other delicacy enters into range, OR when a savory molecule lands on the flicking tongue (vomeronasal organ or “Jacobson’s organ”), STRIKE!

Strike indeed! Strike with the largest fangs of any rattlesnake species and with a venom pact-full of proteins adapted to produce hemorrhaging and tissue necrosis.

Here's a quick video of the same specimen. He's on the move, so I paused the video a couple of seconds at the start; his head is near the upper right-hand corner - look for the curser.

Although the food capturing mode of Crotalus adamanteus can easily be described as “predatory,” their relative contribution, or “predatory influence,” within ecosystems is not especially clear. Typically, when viewing a system’s predator-prey functionality the response and feedback between prey availability (how many are present) is weighed against the number of predators acting antagonistically within the system.

For example, one question that could be posed in regards to the predator function of Crotalus is “how does a surge in rabbit numbers (prey) affect the longevity and reproductive success (population) of the eastern diamondback?” This may seem pretty much straight forward, however; the ability of reptiles to control or impact prey populations within a given environment may be somewhat different than those of endothermic predators; after all, the biology and physiology of ectotherms is considerably different – they posses a different metabolic scheme altogether.

In examination of predator function within the Viperidae (the Family to which the eastern diamondback is a member), Erika Nowak of the US Geological Survey and others concluded that in comparison to predator-prey models established for mammals, the ectothermic vipers contribute a lesser prey population regulating potential.

The reasons for the Viperidae’s decrease in predator functionality include:
1. Longer prey handling times due to a comparatively limited digestive capability
2. Increased tolerances for fasting
3. An increased ability to convert food into fitness currency (progeny)
4. A limited ability for rapid reproductive tracking of short-term prey abundance.

Their article (Functional and Numerical Responses of Predators: Where Do Vipers Fit in the Traditional Paradigms?) Strongly points to the need for additional research in several areas behavioral ecology. I fully agree with this assessment, but for whosoever takes on the task - watch your step!

Erika M. Nowak1, Tad C. Theimer, Gordon W. Schuett (2008). Functional and Numerical Responses of
Predators: Where Do Vipers Fit in the
Traditional Paradigms? Biological Reviews, 83 (4), 601-620

Monday, July 13, 2009

Attack of the Prionus

Prionus imbricornis

The tilehorned root-boring beetle

This guy nearly took out my bedroom window Saturday night; he struck with such an impact I thought that it was a bird…

In the process of the attempted B & E he did manage to clear away a few spider webs though – that’s definitely a plus! The remnants from the web can be seen on his left antenna and thorax.

Prionus imbricornis are active this time of year and are attracted to lights. They’re fairly sizable with lengths over two inches common. They have distinct antennomeres (antenna segments) that can be used to identify the species.

Root boring beetles are sometimes considered to be pests due to the damage they can inflict on hardwood trees.

Wetland Plant of the Week #25

Magnolia virginiana Sweet Bay

Sweet bay is a medium sized Obligate evergreen with alternating leaves. The undersides of the leaves display a white pubescence. Bisexual, showy white flowers are fragrant and appear in the spring. Magnolia love saturated soils but will not tolerate inundation over extended periods.

This one photographed near Big Shoals State Park .

Friday, July 10, 2009

Antibiotics: A Thing of the Past?

Acclaimed scientist and Nobel laureate Kary Mullis details a possible alternative to antibiotics.

Absolutely incredible!

Only about 4 min long:

Thursday, July 9, 2009

Taking a Bite out of Niche Conservatism

In efforts to quash assumptions associated with niche conservatism, scientists from the Florida Museum of Natural History and the New York State Museum have enlisted the teeth of several fossil mammals to better understand the ecology of climate change.

Recently published at PLoS One, the research holds critical the idea that niches remain constant over extended periods of time. This idea, called niche conservatism, essentially holds that niches are highly specialized, ancestrally –linked, relatively inflexible and are therefore exceedingly susceptible to disturbance and rapid degradation in the face of change - particularly climate change.

While biologic response to environmental change is assumed, often such conservatism is overemphasized and is presented in a manner inconsistent with understanding gained through modern ecology and the insights of paleontology, which have both demonstrated incredible plasticity within the Earth’s biota.

Undoubtedly, the changing climate is of great concern and poses tremendous challenges to all organisms, but at the same time life is flexible and extinctions are not entirely unavoidable. As evidence to life’s flexibility, the currently discussed paper uses the testimony of change documented in the isotopic signatures of mammalian tooth enamel to show that the obstacle of climate change has been successfully negotiated in the past. More specifically, glacial-interglacial transitions during the Pliocene and Pleistocene are marked by substantial alterations in plant communities; however the contemporaneous uptake of vegetative food-stuffs by mammals seems to have fluctuated little.

The article is worth a read:
DeSantis, L., Feranec, R., & MacFadden, B. (2009). Effects of Global Warming on Ancient Mammalian Communities and Their Environments PLoS ONE, 4 (6) DOI: 10.1371/journal.pone.0005750

Vertebrates, and in particular mammals, are highly responsive to changes in the environment. Climate fluctuation can lead to an incredible amount of variation in the diet choice, distribution, and even the morphology of vertebrates.

Natural selection is a reflection of the biological and physical environment as transcribed into the genes of flora and fauna; however, the DNA found within living cells functions only as a recipe for ecological fit, the actual ingredients – the building materials - required to construct living tissue are harvested from surrounding chemistry. Because of variability inherit to this chemistry, the isotopic constituents that compose individuals may differ with respect to climate, diet, or a number of other variables.

For example, carbonate apatite - a primary constituent of both skeletal bones and dentition in vertebrates - is incorporated into organisms through diet and water uptake. Some conservationists use the isotopic signatures recovered from this apatite to better decipher the life histories of contemporary species in expectation of aiding in their continued preservation. As a case in point, remains from the world’s largest cavefish (Milyeringa veritas) have been used by Australian conservationists to better examine and comprehend the environment and ecosystem inhabited by the fish. The cavefish resides in deep water columns that are rich in dissolved limestone. Due to relative densities and variable solubility, different depths in the water column are correlated to specific concentrations of dissolved materials. By examining the isotopic signatures of the cavefish’s skeletal apatite, conservationists were able to discover the exact depth the fish occupies.

As demonstrated by the cavefish, uptake of elements within vertebrates (O, C, Sr & others) generates a highly detailed record of the environmentally available isotopes at a given point in time; this availability can even be indicative of climate.As another illustration of application, Thure Cerling and others at the University of Utah have refined the technique of laser ablation to such quality and precision that they can use it to vaporize the apatite found in teeth. They then analyze the resulting gas via spectrometry to determine its isotopic components. The teeth can be examined to such resolution as to be able to report the dietary preferences of mammals between C3 and C4 plants. A similar isotopes-from-enamel strategy was employed by the folks from the University of Florida to expound several fallacies of niche conservatism…

Examinations of isotopic records are commonplace for many paleontologists. Uncountable volumes have been written on Foram O-18 isotopes and their relationship to periods of increased glaciation, and similar correlations of speleothems and C-13, but accurate isotopic records of both of these elements can be obtained from other sources as well - including mammals.

As a side note - skeletal tissues, which possess apatite, are very susceptible to diagenic processes that can cause recrystalization and alter results, but dental samples seem to be far more reliable when it comes to maintaining their original isotopic signatures. This coupled with the knowledge acquired in the past few decades in regarding incorporation of specific O-18 and C-13 isotopes into biological entities has brought to light a highly accurate record of climate change – and the critters that adapted to it.

Tuesday, July 7, 2009

Megacephala in my yard

I was pretty excited to run into this brilliantly colored tiger beetle yesterday evening; just four genera of tiger beetles are found in the United States as a whole - and only two in Florida!

The aptly named Megacephala bears large mandibles which it uses to catch and ravage prey. A nocturnal and opportunistic predator, Megacephala carolina is fleet-of-foot, and as agile as a… Well… As agile as a tiger!

Three varieties of Megacephala are found in Florida: Megacephala virginica, Megacephala carolina floridana (found in South Florida), and of course, Megacephala carolina as shown here from my backyard in Tallahassee.

Sunday, July 5, 2009

Wetland Plant of the Week #24

Sarracenia leucophylla

White top pitcher-plant

The white top pitcher-plant is an Obligate insectivorous member of the Sarraceniaceae Family. It displays alternate and erect green leaves with the upper most tubes/hoods colored white with purple veination; the flowers are dark red or maroon in color.

These were photographed last Thursday in Bay County, near Point Washington Wildlife Management Area.

Friday, July 3, 2009

Cretaceous Billabong Yields New Dinosaurs

Hocknull, S., White, M., Tischler, T., Cook, A., Calleja, N., Sloan, T., & Elliott, D. (2009). New Mid-Cretaceous (Latest Albian) Dinosaurs from Winton, Queensland, Australia PLoS ONE, 4 (7) DOI: 10.1371/journal.pone.0006190

Two newly identified sauropods and a new theropod have been excavated from the base of the Winton Formation near central Queensland. Fossilized pollens in-strata with the vertebrate remains indicate a Phimopollenites pannosus palynomorph Zone sequence and are thought to be Albian in age - about 100 million years old. In regards to ecology, cursory examinations of taphonomy and sedimentology show that the depositional conditions associated with the finds are akin to those found in modern oxbow lakes, or as the Aussies call them “billabongs”.

Although all three dinosaurs represent significant finds, the predatory theropod in particular is sure to bring publicity to the Australian Age of Dinosaurs Museum of Natural History and the Queensland Museum, which jointly worked on the excavations and diagnoses of the dinos. There’s nothing quite like a giant predatory allosauroid in terms of stirring the public’s interest in paleontology and stimulating museum attendance numbers.

According to Ben Kear of La Trobe University in Melbourne, "Australia is one of the great untapped resources in our current understanding of life from the Age of Dinosaurs. The discoveries...will definitely reinvigorate interest in the hitherto tantalizingly incomplete, but globally significant record from this continent..."

Meet “Matilda”

Named for the Diamantina River and one of Austrailia’a National songs (“Waltzing Matilda”), Diamantinasaurus matilda was a 16-meter long (52-foot) sauropod.

Nicknamed Matilda, she is the more stout of the two new sauropods and left behind a variety of fossils, including a pelvis:

Left reconstructed pelvis in lateral (A) view. Left ilium in anterior view (B) showing the position of the sacral vertebrae. Right pubis and ischium in medial (C), proximal (D) and lateral (E) views. Right ischium in lateral (F) and medial (G) views. Reconstructed right and left ischia in dorsal view. Abbreviations: ip, ischial peduncle; iip, iliac peduncle of ischium; of, obturator foramen; pa, pubio-ischial contact; pip, iliac peduncle of pubis; ppd, pubic peduncle; ppp, preacetabular process of ilium; s, sacrum; sym, fused ischial symphysis.

Meet “Clancy”

Wintonotitan wattsi, or “Watts' Winton Giant" was also around 16-meters in length, but sported a more elongate neck than Matilda.

Nicknamed Clancy, he was diagnosed from a variety of fossils, some partially articulated, including several vertebra:

Partial dorsal centrum in lateral (A) and posterior (B) views. Isolated neural spine in anterior view (C). Anterior caudal vertebrae of Wintonotitan wattsi. Anterior caudal vertebra in lateral (D) and anterior (E) views. Anterior caudal vertebra in posterior (F), lateral (G) and ventral (H) views. Anterior caudal vertebra in anterior (I), lateral (J) and ventral (K) views. Abbreviations: plc, pleurocoel; pcdl, posterior centrodiapophyseal lamina; prel, prespinal lamina; spl, spino-prezygopophyseal lamina.

Last, but not least - Meet “Banjo”

Called “Banjo” after Australian bush poet Banjo Patterson, Australovenator wintonensis was a 5-meter long (16-foot), 500 kilogram (1100 pounds) predator with three slashing claws.

"The cheetah of his time, Banjo was light and agile," "He's Australia's answer to Velociraptor, but many times bigger and more terrifying," said the article’s lead author Scott Hocknull of the Queensland Museum.

As evidence of his ferocity, here are a few of Banjo’s teeth:

Isolated teeth in labial (A, C, E, F, G, I, J, L) and labial (B, D, F, H, J, K) views. A–B. Anterior dentary tooth or premaxillary tooth. C–L. Dentary teeth.

Hocknull, S., White, M., Tischler, T., Cook, A., Calleja, N., Sloan, T., & Elliott, D. (2009). New Mid-Cretaceous (Latest Albian) Dinosaurs from Winton, Queensland, Australia PLoS ONE, 4 (7) DOI: 10.1371/journal.pone.0006190

All Images from Referenced Article

Associated Press News

Reuters News

Wednesday, July 1, 2009

Field Photo: Buprestis rufipes

Buprestis rufipes - a jewel beetle - munching on a young oak tree next to the Ochlocknee River near Tallahassee, Florida.

This beetle’s iridescence (sort of washed-out in these pics) isn’t due to pigmentation in the exoskeleton, but rather microscopic textures in its cuticle which reflect and scatter particular frequencies of light.

Wetland Plant of the Week #23

Woodwardia virginica

"Virginia Chain Fern"

Chain ferns are Facultative Wet members of the Blechnaceae Faimily. Their leaves are bright green and display a characteristic "chain like" venation pattern on each pinnule. They are deciduous ferns with an affinity for acidic wetlands with plenty of sphagnum in the groundcover.

These were photographed a couple of weeks back near Big Shoals State Park in Florida.