Thursday, August 27, 2009

A Day at the Carnegie Museum of Natural History

I’ve just returned from a visit to my hometown of East Liverpool, Ohio (my trip north is the reason for the lull in activity here over the past 10 days); although, the majority of my time there was spent visiting with family and catching-up with old friends, I did find the opportunity to travel 45 miles due east to a world renowned museum – the Carnegie Museum of Natural History.

Growing-up an hour’s drive from one of the planet’s largest dinosaur collections was an absolute privilege. I first visited the museum in conjunction with a fifth grade field trip; since that inaugural adventure into the Mesozoic return pilgrimages have been made uncountable times with each stopover as awe-inspiring as the first. Even beyond the dinos, the museum exhibits an extraordinary gem and mineral collection, an Egyptian hall, its own biology field station, and an absolutely fantastic geology section - the kind of place that motivates both kids and adults to engage the world of science.

The museum is stunning; from the entrance greeting by Galileo to the type specimen of Tyrannosaurus rex (CM 9380) the Carnegie is extensive, immaculate and breathtaking - hats off to the museum’s staff, contributors and the city of Pittsburgh.

Pasted below are a few snapshots taken during my visit, there’s also an ABC News video embedded that provides a little more info on the museum’s recent 36-million dollar “Dinosaurs in Their Time” expansion, which strives to display fossils in natural postures and ecosystems.

Tuesday, August 11, 2009

The Metacommunity Mannerisms of Foraging Frogs

Last Saturday, snapshots of a spring peeper (see A Peeper’s Problem) were used to springboard a discussion regarding habitat fragmentation and the conservation of species that exhibit behavioral characteristics not exclusively bound to a single ecological community type. The general idea was that saving a forest from commercial harvest, or conserving a wetland, is an essential step towards preserving biodiversity; however just as important to conservation efforts is the protection of wildlife corridors and other thoroughfares used by flora and fauna. In that post, the spring peeper was forwarded as an exemplar of a species whose natural history requires spatial dispersion between differing communities; those communities used for reproduction (wetlands) and those used during non-reproductive adulthood (forests). To further delineate the “metacommunity” concept, the current post aims to look at this idea through the bulging eyes of a different, though not wholly dissimilar, species – the squirrel frog.

As fate would have it, on the very same stormy night that the peeper was victimized by the paparazzi, another frog also happened into the viewfinder – as though he knew that a herpetologically-laden week of community ecology discussions at Ecographica was eminent…

Meet Hyla squirella, the squirrel frog:

The squirrel frog is common throughout the Southeastern United States and like Pseudacris crucifer, Hyla squirella is a terrestrial tree frog that undertakes journeys from “water-to-wood and back again” during its life cycle. These travels are bound to reproduction and early development in water, with maturation and adulthood driving them to arboreal existence in the uplands.

Metamorphosis from tadpole to froglet is the starter pistil for transitioning to the trees, with seasonality - specifically the rainy season - as one of the big signals for movement water-ward. Thus, H. squirella represents a biological link between two ecologically distinct communities; a wetland with depressional geomorphological features that are awash in aquatically adapted plants, invertebrates and fish with fluctuating levels of hydrology and nutrients, VERSUS a forest system with epiphytic plants, wood boring insects and a generally more arid microclimate.

A set of distinct ecological communities that are biologically entangled through the spatial dispersion of commonly hosted, interacting species is one way of defining the term “metacommunity.” Essentially, a metacommunity is an order of ecological organization above the community level. So, moving backwards through the hierarchy, a metacommunity is a set of distinct communities, a community is a set of distinct populations and a population is a set of individuals. And, just as individuals interact and associate with each other under rules established by population dynamics, communities can interact with each other in a landscape through processes that can be described in terms of a metacommunity dynamic.

In traversing ecologically unique community structures, the niche of the squirrel frog presuppose many risks inherit to a world of pavement and progress, but Hyla squirella enters the battle well equipped and is armed with the decision making tools afforded by natural selection.

For example, during ovipositioning the squirrel frog deposits its eggs in elongate, slender strings with each egg lined-up, one after the other, like dominos made of pearls; these strings are laid in waters that have been positively selected for their ability to supply young tadpoles with the resources required for growth and development. For the herbivorous Hyla tadpoles, this means that an abundance of algae, plants and inorganics can be found attached to submersed logs, rocks and other structures. The tads are suspension feeders; this means that they scour the surface of substrates for nutrients, akin to tiny vacuum cleaners, leaving no surface un-sampled. Although food acquisition is vital to the tadpoles ultimate success, another key decision also enters into the equations of the mother frog’s evolutionarily provided calculator – predator avoidance.

In considering the processes under which metacommunal species weigh the risk of death against the benefits of nutrient availability (growth) within a given habitat, C.A. Binckley (Old Dominion University) and W.J. Resetarits (University of Southampton) examined the squirrel frog’s preferences in natal ponds. They constructed 54 experimental ponds in which they controlled nutrient availability and the occurrence of fish that prey on hylid eggs. By comparing the total eggs deposited at each artificial pond, they were able to correlate the pond preference of mother frogs for expressed nutrient availability and predatory risk. Their study demonstrated that within a variable landscape, metacommunal species display habitat choosing behaviors that are in accordance with optimization theory and predicted foraging behavior. In other words, the research showed that the squirrel frogs exhibited a pond choosing behavior which can be affectively viewed as the frog weighing the risk of death against the opportunity for growth; with the frog trying to achieve the lowest possible “mortality /growth” value.

In a similar fashion, it’s a safe bet that similar “decisions” are undertaken by H. squirella when choosing upland habitats as an adult… The decision making toolset programmed into the genes of the squirrel frog not only provides the ability to survive and excel within a variety of community types, it also is the instrument through which communities as distinctive as wetlands and upland forests are linked. Alteration of one habitat, one species, or even one gene, can have reverberations in far ranging ecosystems; this is precisely why conservation of those connections is of the utmost importance.

Binckley, C., & Resetarits, W. (2008). Oviposition behavior partitions aquatic landscapes along predation and nutrient gradients Behavioral Ecology, 19 (3), 552-557 DOI: 10.1093/beheco/arm164

Monday, August 10, 2009

The Threatened Gopher Tortoise

Sticking with the herpetological theme of the last couple of narrative posts (Diamondback Rattle Snakes and Spring Peepers), I thought that I’d share a couple snapshots and a short video clip of a gopher tortoise from a couple of weeks back.

This gopher tortoise, Gopherus polyphemus, was photographed in west-central Florida just outside of a planted slash pine plantation.

Most of the pine plantations in Florida have resident gopher tortoises; however these areas of anthropogenic alteration are far from ideal habitats. The plantations aren’t good for the tortoises primarily because of the fact that the plantations were established for commercial use (wood production) and were therefore seeded very densely to maximize the quantity of trees grown. The extreme density of the canopy trees drastically reduces the amount of light reaching the forest floor and affectively minimizes herbaceous growth and groundcover which the tortoises consume.

In addition to silvaculture (and as with the spring peepers), gopher tortoise populations are also heavily impacted by habitat fragmentation, which is one reason why they are listed as a Threatened Species by the U.S. Fish and Wildlife Service.

Here's a quick video of the above tortoise racing to his burrow:


For those that may not be familiar with the gopher tortoise, here’s a pile of info snagged from the Smithsonian Marine Station’s website:

The gopher tortoise, Gopherus polyphemus, is a large terrestrial turtle having forefeet well adapted for burrowing, and elephantine hind feet. The front legs have scales to protect the tortoise while burrowing. Body length averages approximately 25 cm (10 inches), with the shell ranging in height from 15 – 37 cm (6 – 15 inches). Body mass averages approximately 4 kg (9 pounds). Color is a dark brown to gray-black, with a yellow plastron (bottom shell). A gular projection is evident on the anterior plastron where the head projects out from the shell. Sexual dimorphism is evident, with male gopher tortoises having concave plastrons, while those of females are flat. In addition, the gular projection on male plastrons is generally longer than in females (Ernst and Barbour 1972).

Gopher tortoises dig burrows for cover and for nesting. These can be extensive, measuring approximately 4.7 - 11 m (14 – 40 feet) in length (Witz et al. 1991). Burrow depth is heavily dependent on depth of the local water table (Diemer 1986; Burke and Cox 1988).

Trophic Mode:
Gopher tortoises are primarily herbivorous, with the bulk of the diet consisting of low-growing herbs and grasses. Foods most common in the diet are grasses and legume fruits. They are also known to consume pine needles and seeds, oak mast, prickly pear cactus, asters, palm tree fruits, raspberries, black cherry, and gopher apples (Landers et al. 1980; Auffenberg and Franz 1982; Diemer 1986). Gopher tortoises have also been observed to eat mollusk shells and the bones of dead animals, possibly to supplement their diets with additional calcium.

Predators of gopher tortoises include various snakes, fire ants (Solenopsis saevissima), accipiter hawks, buteo hawks, raccoons, opossums, armadillos, skunks, dogs, foxes, feral cats and man all prey on gopher tortoises. Generally, eggs and hatchling tortoises are significantly more at risk for predation than older animals.

Gopher tortoises use a variety of habitats, including beach dunes, scrub, and pine flatwoods. In all habitat types, soils are generally dry, sandy and well-drained. While generally avoiding swampy areas, gopher tortoises in Brevard County, Florida have been observed to inhabit poorly-drained scrub and slash pine flatwoods (Breininger et al., 1991). In this county, higher densities of gopher tortoises were found in poorly-drained sites than in well-drained sites.
Individuals occupy distinct home ranges, with male home ranges typically being larger than those of females. In east-central Florida, home ranges of male tortoises averaged 1.9 ha (4.7 ac), while those of females averaged only 0.65 ha (1.6 ac). A tortoise excavates several burrows for its use within the home range. Burrows typically are dug at a 30 degree angle from the surface. In Florida studies, male tortoises dug between 8 – 35 burrows. Females tended not to use as many burrows as males, averaging between 3 – 17 burrows (Breininger et al., 1988).

Tortoise densities tend to be higher in fire-adapted communities (Auffenberg and Franz 1982; Diemer 1986). In the absence of fire, canopy trees grow large and shade out the herbaceous vegetation that gopher tortoises rely on as their primary food source.

Associated Species:
Gopherus polyphemus is considered a keystone species in that more than 80 different species live in their burrows, or are dependent on their burrows for protection. Some of these species, such as the gopher frog (Rana areolata), the pine snake (Pituophis melanoleucus) the indigo snake (Dymarchon corais), the scrub jay (Aphelocoma coerulescens) and in inland prairies, the burrowing owl (Athene cunicularia floridana) are rare (Burke and Cox 1988; Spillers and Speake 1988; Stout et al. 1988;Witz et al. 1991).

Sunday, August 9, 2009

VIDEO: Biomimicry in Action

Although the point of this talk is demonstrate how the natural world can provide design models for advances in human technology, what I really enjoyed about it was the awe-inspiring adaptations shown by the critters of interest – useful to humans or not. And, the image of the kingfisher diving is awesome!

From TED
Janine Benyus has a message for inventors: When solving a design problem, look to nature first. There you'll find inspired designs for making things waterproof, aerodynamic, solar-powered and more. Here she reveals dozens of new products that take their cue from nature with spectacular results.

Saturday, August 8, 2009

To the Woods and Back Again; the Peeper’s Problem

I photographed this “spring peeper” a few nights ago following a fairly impressive thunderstorm. The squall dumped a substantial amount of rain and provided Pseudacris crucifer with the perfect opportunity to talk-up the local ladies. His easily distinguished high pitched “peep –like” call is what brought him to my attention; though distinguished as his call was, he certainly had his work cut out for him on this particular night because the yard was alive with the chorus of his rivals.

Pseudacris crucifer is common throughout the eastern half of the United States and their range extends northward into Canada. Adults grow to a length of about three and a half centimeters, and as seen in the photos, their skin is a light olive-brown color with striped designs across the legs, a darker toned “X” pattern on their back and generally a darker brown color around the eyes (still visible but washed-out in these photos).

Being a terrestrial tree frog, the spring peepers have natural history requirements that depend on access to both water and forested areas. Their life cycle takes them from the vernal pools and road side ditches of their tadpole-hood to trees and shrubs as adult frogs. As with most frogs, water is a requirement for reproduction, however peepers don’t require permanent water bodies, and they are perfectly content to use puddles, seasonal ponds and even the water held between the boughs and stems of trees for ovipositioning. Once reaching adulthood, peepers travel to forested areas to hunt insects along the multitudes of woody tree branches, and to hide from predators amongst the leaves. Then, after obtaining sexual maturity, they make seasonal treks back to the water in order to start the cycle a new.

As briefly described above, the life cycle of Pseudacris crucifer necessitates the undertaking of a certain amount of risk… Traveling from water to wood and back again can be a perilous journey, not only because of natural predators, but also because of the increasing levels of habitat fragmentation at the hand of human productivity. More specific to the travels of the spring peeper, the removal of adult habitat through deforestation and the construction of paved roads represent tremendous hazards to species conservation.

Scientists from the Geomatics and Landscape Ecology Research Laboratory and Lakehead University weighed the effects of increased vehicular traffic against the impacts associated with deforestation relative to the life cycle of six anuran different species. The researchers conducted amphibian surveys at thirty-six ponds and then sorted their field data based on the ponds’ proximities to areas of high and low vehicle traffic as well as the nearness to varying densities of forest. What they discovered was that although some variation in the impacts of traffic-Vs-deforestation exited between species, overall both the removal of forest habitat and mortality as a result of road kill appeared to detrimentally affect anuran success. In regards to the spring peepers surveyed as part of this study, the quantity and proximity of forest cover was found to be of higher significance than was the density of roads and associated traffic – though both of these human influenced factors generated damaging impacts in the productivity of Pseudacris crucifer.

In considering the spring peeper’s natural history and the goals of conservation, organisms which are not tightly bound to a single community type, and are rather found to exist within a metacommunity dynamic, require special attention by biologists. Due to their fluctuating life requirements, that change from birth-to-adulthood and vary between wetland and forested habitats, the unique immigration and emigration patterns exhibited by the species require preservation of forest and water resources as well as protection of the wildlife corridors and resource connectivity between the two.

EIGENBROD, F., HECNAR, S., & FAHRIG, L. (2008). The relative effects of road traffic and forest cover on anuran populations Biological Conservation, 141 (1), 35-46 DOI: 10.1016/j.biocon.2007.08.025

Friday, August 7, 2009

Wetland Plant of the Week #25

OK, maybe the workload has dissipated enough to drop a couple of posts here at Ecographica…

To get back things back on track, let’s first get caught-up with the Wetland Plant of the Week. Back in early July we left off with Sarracenia leucophyll, the white top pitcher plant, so let’s start there with another species of Sarracenia, the “trumpet-leaf pitcher plant.”

Sarracenia flava

Trumpet leaf pitcher plant

The trumpet-leaf, like the white top, is an insectivorous plant in which the leaves have adapted to form a “cup” capable of holding water. The trumpet-leaf has yellowish green pitcher leaves and hoods with a maroon colored interior neck. The hood stretches over the mouth of the “pitcher cup” but does not completely close it. The flowers are yellow in color, solitary and persistent. This pitcher plant is an Obligate species and is found in bogs and wet savannas.

This one was photographed near Panama City last Wednesday.