Effects of fine‐scale forest habitat quality on movement and settling decisions in juvenile pond‐breeding salamanders

Abstract

A better understanding of how individuals respond to variation in habitat quality while moving through heterogeneous habitats is needed to predict ecological phenomena at larger scales, such as local population and metapopulation dynamics. We sought to identify how fine‐scale habitat quality affects the decisions of juvenile pond‐breeding salamanders (Ambystoma maculatum and A. annulatum) to cease dispersive movements away from their natal pond, select a refuge, and settle. Because of the acute susceptibility of juvenile amphibians to evaporative water loss in terrestrial habitats, we predicted that they possess mechanisms for adjusting their behavior in response to variations in fine‐scale habitat quality. We used experimental field enclosures to isolate the effects of habitat quality on settling behavior and employed generalized linear mixed models to examine how manipulations in canopy cover (closed or open) and microhabitat (control, compacted soils, high coarse woody debris, high burrow density), along with environmental variables (rainfall and air temperature), affect the individual's probability of settling. Our results indicated that A. maculatum and A. annulatum had a 10% and 30% decreased probability of settling in open‐canopy clearcut habitat, respectively, compared to closed‐canopy forest habitat. In addition, A. annulatum were 24% less likely to settle in compacted soil treatments. Although the settlement probability of A. annulatum did not depend on refuge availability, A. maculatum were 18% and 25% more likely to settle under conditions of high burrow density and high coarse woody debris, respectively. These findings make a unique contribution to our understanding of amphibian movement ecology by demonstrating how the interplay of external factors and individual behavior produce observed patterns of movement and habitat selection.

The effects of conspecifics on burrow selection in juvenile spotted salamanders (Ambystoma maculatum)

“…Field studies versus artificial laboratory experiments may yield greater insight on burrow selection behavior and the potential benefits to the use of social cues during dispersal (Regosin et al 2004). Unlike salamanders in the adult stage, who likely focus on resource acquisition within permanent refugia sites, salamanders in the juvenile stage must assess habitat quality as they move through heterogeneous landscapes in order to locate suitable refugia (Roberts and Liebgold 2008;Osbourn et al 2014). The spatiotemporal dynamics of salamander populations are dependent on the dispersal mechanisms and the interactions of juveniles in conjunction with the environment, available resources, and other organisms.…”

“…1). Artificial burrows were constructed from PVC pipes (1.9 cm inner diameter, 2.54 cm outer diameter, 7 cm long, with a 30°angle cut at one end; Osbourn et al 2014) and placed at a 30°angle in the polyurethane foam (Fig. 1).…”

The Importance of Maintaining Upland Forest Habitat Surrounding Salamander Breeding Ponds: Case Study of the Eastern Tiger Salamander in New York, USA

“…Smaller juveniles may not have the water or fat reserves necessary to move great distances, so if individuals can survive staying closer to the breeding pond, the more abundant food availability would allow them to continue growing at a faster rate post-metamorphosis [52,53,61,62,68]. Larger juveniles are able to move larger distances from the breeding ponds upon emigration, likely due to higher body water and fat reserves (i.e., lower surface area to volume ratio), and optimal time for larval development [52,53,68]. Body size of juvenile amphibians has been linked to the temperature and hydroperiod of a natal pond, indicating the importance of maintaining optimal wetland hydroperiods sufficient for full larval development [69].…”

“…Second, we hypothesized that a percentage of juveniles would travel farther than the adults, since some juveniles disperse to other wetlands from the natal wetland, rather than simply emigrating, creating a need for safe dispersal routes connecting wetlands [50,51]. Third, we predicted that the distance moved by juveniles would vary by body size, because larger juveniles could have more energy reserves and be less vulnerable to dehydration during movement [52,53]. Fourth, we predicted that since habitat characteristics affect emigration movements [3,12,40], adult and juvenile tiger salamanders would select refugia within the forested pitch pine-oak forest.…”

Buffer-Mediated Effects of Clearcutting on In-Pool Amphibian Productivity: Can Aquatic Processes Compensate for Terrestrial Habitat Disturbance?

“…Given their bi-phasic life histories, clearcutting could impact eggmass and metamorph production directly by changing environmental conditions in ephemeral pools and/or indirectly by altering the surrounding terrestrial habitat, causing adult amphibians to invest less of their energetic resources in reproduction and/or reducing breeding-population size through increased terrestrial-phase mortality and/or dispersal out of the population [31,32]. Ephemeral pools are complex systems, however, with dynamic food webs [28,33,34], competitive interactions [35][36][37], and high intra-and inter-annual variability [23,28,38].…”