From Habitat to Hormones: Year-around territorial behavior in rock-dwelling but not in forest and grassland lagomorphs and the role of DHEA

Year-around defense of extremely patchy habitat may require hormones that drive territorial behavior, but have no other costly physiological effects. The American pika (Ochotona princeps), but not the snowshoe hare (Lepus americanus) nor the eastern cottontail rabbit (Sylvilagus floridanus), exhibits this behavior. The former engages in contest competition against all individuals independent of sex to protect its territory in highly fragmented patches on mountain talus slopes; the latter in scramble competition in more continuous forests, grasslands, and shrublands. The hormonal basis for this difference in lagomorphs is unknown. Dehydroepiandrosterone is a prohormone produced by the zona reticularis of the adrenal cortex. It has no effect on aggressive behavior until converted in the brain to estrogen. We assessed levels (DHEA-S plus DHEA) in all species collected in the wild. In nonbreeding pikas, levels were 256 times higher than in hares and 22 times higher than in rabbits. Within species, females and males had similar levels. The proportion of the adrenal cortex devoted to the zona reticularis was significantly larger in pikas than in hares or rabbits. Our evidence is consistent with the hypothesis that dehydroepiandrosterone drives this individual-based, year-around territoriality in pikas. We propose a definitive experiment to determine this and recommend comparative studies in central Asia where there is high diversity of pika species whose behavior ranges from individual-based territoriality to colonial. Thus, we speculate that the wild American pika has the adrenal-brain nexus for all seasons and is an excellent model to understand how habitat drives the hormonal control of spacing behavior.

Snail leaps and bounds: drivers of the diel movement pattern of a large invertebrate, the Caribbean queen conch (Lobatus gigas), in a marginal inshore habitat

Understanding the relationship between the movements of animals and their environment is crucial for fisheries and species management. There is currently a lack of detailed information about the movement of slow-moving benthic species, especially for species of ecological or commercial importance. Here we document the relationship between diel movement and environmental parameters in a groundwater-fed coastal inlet for the queen conch (Lobatus gigas (Linnaeus, 1758)), an important fishery resource of the Caribbean region, using three-dimensional accelerometers and video cameras. Our results show immature queen conch (n = 9) spend most of their active time grazing, exhibiting two main distinct movements that we characterize as a leap and a drift that are mostly used to access new foraging resources. When overturned, they flip, producing a movement with the highest acceleration recorded to limit exposure and restore normal position. Movement patterns appear to be significantly affected by the oxygen concentration of the bottom water, with lower activity during low-oxygen levels in the morning (probability of 0.75 of observing 0 movement per hour) and maximum activity during the afternoon when oxygen concentration is at its maximum (probability of 0.80 of observing >10 movements per hour). Salinity and temperature had little effect on movement patterns. Our results confirm that highly variable marginal habitats like groundwater-fed inlets are suitable for juvenile conch growth and should be included in efficient conservation plans.

A landscape genetic analysis of swamp rabbits (Sylvilagus aquaticus) suggests forest canopy cover enhances gene flow in an agricultural matrix

Habitat loss and fragmentation pose a continued and immediate threat to wildlife and create a persistent need for ecological information at the landscape scale to guide conservation efforts. Landscape features influence population connectivity for many species and genetic analyses can be employed to determine which of these features are most important. Because population connectivity through dispersal is important to the persistence of swamp rabbits (Sylvilagus aquaticus (Bachman, 1837)) at the northern edge of their range, we used a landscape genetic approach to relate gene flow to landscape features that may impact dispersal success. We tested resistance values for attributes of land cover, watercourse corridors, canopy cover, and roads and used causal modeling and redundancy analysis to relate these representations of landscapes to genetic distance for swamp rabbits in southern Illinois, USA. Models that included canopy cover had the strongest correlations with genetic distance and were supported by our methods whereas other models were not. We concluded that high tree canopy cover enhances gene flow and landscape connectivity for swamp rabbits in southern Illinois. Our study provides important empirical evidence that landscape variables may impact the habitat connectivity of swamp rabbits. Preserving dispersal routes for swamp rabbits should focus on improving canopy cover, in both bottomland and upland, to connect suitable habitat.