Blog Post Two: Preliminary Movement Patterns

Hello Again!

As always, the past two weeks have been filled with tracking! We also tagged a few more pickerel frogs during a large rainstorm last week, as the wet conditions brought them out in full force! Most species will begin migrating away from breeding ponds soon, making it more difficult to track them, so bolstering our sample size now gives a cushion in case we lose any individuals during their journeys.

Now that we have been following frogs for so long, some broad behavioral patterns are already becoming clear. Species of the genus Anaxyrus (American and Fowler’s toads) have proven to be the most surprising species to follow, as they have overturned many of my initial hypotheses. Before conducting this study, I predicted to find them frequently associated with coarse woody debris such as logs, however 90% of the time we locate them, they are simply hiding in shallow leaf litter. Additionally, we have noticed that they nearly always are associated with steep slopes, and tend to avoid flat ground. This may be because leaf litter tends to accumulate on slopes, or possibly because slopes tend to have more moist conditions due to rain drainage. Because I am taking both leaf litter and soil moisture measurements, I will be able to assess if either of these theories hold true when I conduct data analysis.

Two distinct types of individuals have begun to emerge among the toads as well. There are “roamers,” which tend to move large distances day-to-day and rarely return to the same spot, and there are “homebodies” which stay within a very small area, and frequently return to the same location or refuge. These differences in behavior may have to do with foraging ability or predator avoidance techniques.

Pickerel frogs have also proven to be very interesting due to their tendency to make terrestrial forays. Though they are of the genus Lithobates, a typically aquatic associated species, many individuals have made extended movements away from water during periods of high rain. It is likely that I will be able to demonstrate this activity by correlating their movement distances with soil moisture. It is still unclear whether these forays are linked to foraging behavior or something else, however.

Green tree frogs have been the least mobile species thus far, generally remaining within 10-15 m of their breeding pond and rarely leaving the same tree. As these frogs are still in the breeding season, it makes sense that they would remain near their ponds. Interestingly, however, Fowler’s toads, which also are in their breeding season, have not demonstrated this level of site fidelity. It will be interesting to see if the tree frogs maintain this pattern of movement as the breeding season winds down.

As is the nature of field work, we have had to continue making adjustments as problems arise as well. One problem we encountered was realizing that we were beginning to have an effect on the habitat in places that we visited every day (i.e. when monitoring “homebody” toads). In the process of measuring leaf litter and soil moisture, we found that over time we would begin to trample the leaf litter and vegetation in the area. To prevent this, we decided that if a frog remained in the same exact place for multiple days in a row, we would only measure soil moisture and leaf litter once instead of every day.

Additionally, we have decided to focus our efforts only on Green Tree Frogs, Pickerel Frogs, and Anaxyrus toads. Though we initially tagged Cope’s Grey Tree Frogs and Southern Leopard Frogs early in the season, we have found that they are simply too good at slipping out of their transponders for us to warrant tracking them. Southern Leopard Frogs we believe are able to swim out of their belts, and Cope’s Grey’s we believe frequently slip out of their belts during a camouflaging behavior that involves making themselves very flat. Even though we are not able to track these species, however, this is still valuable data to have gathered because our tracking method is novel for use in anurans, and has never been applied to these species before. By assessing its usefulness on these species, we will be able to inform future researchers seeking to use or to improve this method.

In the following weeks, we will continue to track the individuals we have, and I will also begin analyzing the data we have collected this summer. Analysis will involve correlating microhabitat with daily movements and determining home ranges. I cannot wait to see if my field observations hold up in the data, and what other patterns may emerge during the analysis! Hopefully, the patterns we find will produce useful tools to managers seeking to improve connectivity between populations of these species.

Until the next post!

-Courtney

Speak Your Mind

*