John D. Scasta | Geology Reports

USGS2021

Body size and digestive system shape resource selection by ungulates: A cross-taxa test of the forage maturation hypothesis

The forage maturation hypothesis (FMH) states that energy intake for ungulates is maximised when forage biomass is at intermediate levels. Nevertheless, metabolic allometry and different digestive systems suggest that resource selection should vary across ungulate species. By combining GPS relocations with remotely sensed data on forage characteristics and surface water, we quantified the effect of body size and digestive system in determining movements of 30 populations of hindgut fermenters (equids) and ruminants across biomes. Selection for intermediate forage biomass was negatively related to body size, regardless of digestive system. Selection for proximity to surface water was stronger for equids relative to ruminants, regardless of body size. To be more generalisable, we suggest that the FMH explicitly incorporate contingencies in body size and digestive system, with small-bodied ruminants selecting more strongly for potential energy intake, and hindgut fermenters selecting more strongly for surface water.

Ecology Letters↗

USGS2019

Black-tailed prairie dog, Cynomys ludovicianus (Sciuridae), metapopulation response to novel sourced conspecific signals

Aggregation of territorial individuals within a species can be facilitated via conspecific signals, wherein settlement implies habitat suitability, ease of resource acquisition and/or increased predator detection. The black-tailed prairie dog is a colonial small mammal with alarm vocalizations that confer benefits via group vigilance against predators and increased foraging time. Although prairie dog alarm calls are relatively well understood, the information embedded in their jump-yip call, which includes both a distinct cry and a bodily gesture, remains less clear. We evaluated prairie dog behaviour in response to conspecific acoustic signals using playbacks of alarm and jump-yip calls at 26 sites in northeastern Wyoming, U.S.A. Recorded calls from an isolated colony were broadcast to a mean of five individuals per site, and behavioural responses were compared against uninfluenced behaviour and a control playback of ambient sounds. The alarm playback caused prairie dogs to increase vigilance 122% and decrease foraging time 23%, demonstrating prairie dogs will shift behaviour based on signals from individuals of an unfamiliar colony. However, the alarm call playback reduced frequency of the jump-yip behaviour only at colonies nearest the recording source. The jump-yip playback caused unfamiliar prairie dogs to display 339% more jump-yips than uninfluenced behaviour. The jump-yip playback did not alter recipients' foraging or vigilance behaviours relative to control treatments, suggesting that although prairie dogs can understand and reciprocate an unfamiliar, single modality signal, they may not shift other behaviours based on this stimulus. As such, the purpose and benefits of the jump-yip call remain unclear. Playback efficacy also had a nonlinear relationship with distance from recording source. Our work improves understanding of communication at the metapopulation level, examines the potential role of the jump-yip and provides insights for how conspecific signals might be used as a management tool.

Wyoming↗