Early development of vocal interaction rules in a duetting songbird

This work was supported by the Maytag Endowment from the University of Miami, a Research Grant from the Animal Behavior Society, a Research Grant from the Organization for Tropical Studies and a Doctoral Dissertation Improvement Grant by the National Science Foundation awarded to K.D.R.-C., and funds from Pacific University and the M.J. Murdock Charitable Trust to C.N.T.Exchange of vocal signals is an important aspect of animal communication. Although birdsong is the premier model for understanding vocal development, the development of vocal interaction rules in birds and possible parallels to humans have been little studied. Many tropical songbirds engage in complex vocal interactions in the form of duets between mated pairs. In some species, duets show precise temporal coordination and follow rules (duet codes) governing which song type one bird uses to reply to each of the song types of its mate. We determined whether these duetting rules are acquired during early development in canebrake wrens. Results show that juveniles acquire a duet code by singing with a mated pair of adults and that juveniles gradually increase their fidelity to the code over time. Additionally, we found that juveniles exhibit poorer temporal coordination than adults and improve their coordination as time progresses. Human turn-taking, an analogous rule to temporal coordination, is learned during early development. We report that the ontogeny of vocal interaction rules in songbirds is analogous to that of human conversation rules.Publisher PDFPeer reviewe

Evolution of Female Preference for Younger Males

Previous theoretical work has suggested that females should prefer to mate with older males, as older males should have higher fitness than the average fitness of the cohort into which they were born. However, studies in humans and model organisms have shown that as males age, they accumulate deleterious mutations in their germ-line at an ever-increasing rate, thereby reducing the quality of genes passed on to the next generation. Thus, older males may produce relatively poor-quality offspring. To better understand how male age influences female mate preference and offspring quality, we used a genetic algorithm model to study the effect of age-related increases in male genetic load on female mate preference. When we incorporate age-related increases in mutation load in males into our model, we find that females evolve a preference for younger males. Females in this model could determine a male's age, but not his inherited genotype nor his mutation load. Nevertheless, females evolved age-preferences that led them to mate with males that had low mutation loads, but showed no preference for males with respect to their somatic quality. These results suggest that germ-line quality, rather than somatic quality, should be the focus of female preference in good genes models

High elevation watersheds in the southern Appalachians: Indicators of sensitivity to acidic deposition and the potential for restoration through liming

Southern Appalachian high elevation watersheds have deep rocky soils with high organic matter content, different vegetation communities, and receive greater inputs of acidic deposition compared to low elevation sites within the region. Since the implementation of the Clean Air Act Amendment in the 1990s, concentrations of acidic anions in rainfall have declined. However, some high elevation streams continue to show signs of chronic to episodic acidity, where acid neutralizing capacity (ANC) ranges from 0 to 20 µeq L-1. We studied three 3rd order watersheds (North River in Cherokee National Forest, Santeetlah Creek in Nantahala National Forest, and North Fork of the French Broad in Pisgah National Forest) and selected four to six 1st order catchments within each watershed to represent a gradient in elevation (849–1526 m) and a range in acidic stream ANC values (11–50 leq L-1). Our objectives were to (1) identify biotic, physical and chemical catchment parameters that could be used as indices of stream ANC, pH and Ca:Al molar ratios and (2) estimate the lime required to restore catchments from the effects of excess acidity and increase base cation availability. We quantified each catchment’s biotic, physical, and chemical characteristics and collected stream, O-horizon, and mineral soil samples for chemical analysis seasonally for one year. Using repeated measures analysis, we examined variability in stream chemistry and catchment characteristics; we used a nested split-plot design to identify catchment characteristics that were correlated with stream chemistry. Watersheds differed significantly and the catchments sampled provided a wide range of stream chemical, biotic, physical and chemical characteristics. Variability in stream ANC, pH, and Ca:Al molar ratio were significantly correlated with catchment vegetation characteristics (basal area, tree height, and tree diameter) as well as O-horizon nitrogen and aluminum concentrations. Total soil carbon and calcium (an indicator of parent material), were significant covariates for stream ANC, pH and Ca:Al molar ratios. Lime requirement estimates did not differ among watersheds but this data will help select catchments for future restoration and lime application studies. Not surprisingly, this work found many vegetation and chemical characteristics that were useful indicators of stream acidity. However, some expected relationships such as concentrations of mineral soil extractable Ca and SO4 were not significant. This suggests that an extensive test of these indicators across the southern Appalachians will be required to identify high elevation forested catchments that would benefit from restoration activities

GPS Technology Reveals Larger Home Ranges for Immature Gopher Tortoises

Movement data and estimation of home-range sizes provide insight into the types and amount of habitat needed to support wildlife populations, which is critical for conservation planning. Gopher Tortoises, which are important ecosystem engineers and keystone species across the southeastern United States, are experiencing ongoing population declines and warrant additional habitat protection and management throughout their range. Conservation assessments for Gopher Tortoises are currently limited by scant knowledge of the ecology of younger age classes. We implemented a short-term study of immature Gopher Tortoise spatial ecology at Archbold Biological Station (ABS), Florida to determine home-range size, movements, and activity levels of 3-7-yr-old tortoises. We used GPS technology to obtain high-resolution temporal tracking data (approximately 10-fold increase compared with the radio tracking frequency in prior studies). Despite the relatively short duration of our study (<= 40 d), immature Gopher Tortoises (n = 6) at ABS had home-range sizes ranging from 0.38 to 1.46 ha, which are approximately 6.6-fold larger than previously reported annual home-range estimates. Tortoises also left their burrows more often (4.0 +/- 3.2 SD times per day) and for longer duration (31.5 +/- 10.6 SD min per emergence) than in studies conducted elsewhere (1.6 times and 18.8 min, respectively). Our results illustrate the importance of employing new technologies to track previously difficult-to-observe life stages and improve conservation efforts for imperiled species

Localities

List of 1627 localities used to generate the Maxent models in "Do ecological niche models accurately identify climatic determinants of species ranges?" Provided data include the longitude and latitude for each locality and bioclimatic variables ('bio1' to 'bio19'), as extracted from the 'WorldClim' database (for definitions see: http://www.worldclim.org/bioclim). Further information about WorldClim at Hijmans, R.J., S.E. Cameron, J.L. Parra, P.G. Jones and A. Jarvis, 2005. Very high resolution interpolated climate surfaces for global land areas. International Journal of Climatology 25: 1965-1978. http://dx.doi.org/10.1002/joc.127

Microhabitat use and migration distance of an endangered grassland amphibian

► Most detailed look to date at habitat use of a grassland amphibian. ► Unlike most amphibians, Ambystoma californiense use the driest microhabitats. ► Spatial and temporal variation interact to affect their distribution. ► Second highest migration distance reported in a salamander. ► Habitat use differs between salamander age classes. There have been many studies of microhabitat use in forest-dwelling amphibians, but very few for grassland specialists. This study examines habitat use of the endangered California tiger salamander (Ambystoma californiense), which inhabits grasslands in California’s Great Central Valley. We used an extensive drift fence array to capture most of the surface-active salamanders over 2years at two adjacent breeding ponds in a natural prairie ecosystem. Model selection using simultaneous autoregressive models was used to generate models describing the microhabitat use of each of three salamander age classes (adults, juveniles, and metamorphs). Adults tended to use microhabitats with flood intolerant vegetation and juveniles were most often found at higher elevation sites; both of these surprising results suggest that California tiger salamanders favor the driest microhabitats in the prairie. For certain comparisons, significant interaction terms indicated that there is both temporal and spatial heterogeneity in the distribution of A. californiense with respect to proximity to breeding ponds. A literature review indicated that A. californiense have the second longest migration distance reported for any salamander (median=556m) and the longest among ambystomatids. Our results emphasize the importance of replicating landscape ecological studies over sites and years, particularly for endangered taxa where effective management hinges on understanding the variability in habitat use across time and space. They also suggest that habitat use of grassland amphibians may be fundamentally different from that of forest-dwelling amphibians in that they require larger terrestrial buffers and use different microhabitats within those buffers