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

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