COS 158-2 - Refined prey selection models at the prey demographic level

Abstract: Traditional prey preference models are crude, estimating prey availability using ¾ adult female body mass. This reflects the presence of neonates, juveniles, sub-adults, and adults in prey populations. Given that predators may target specific demographic classes depending on prey reproductive cycles, these coarse models do not predict preferences for different prey demographic classes. This reduces our ability to predict predator impacts on prey and carrying capacity for predators. We refined prey selection models for two model predators with contrasting hunting strategies – cheetah and lion – by comparing age-specific prey use and seasonal shifts in availability of prey demographic classes. We determined prey use for four male and two female cheetahs, and two male and four female lions fitted with GPS collars via direct observation and GPS cluster analysis. Prey availability was estimated for different demographic classes from monthly driven transects. Seasonal shifts in use of prey demographic classes resulted in contrasting demographic-specific prey preferences for cheetah and lion. Cheetah preferred neonates, juveniles, and sub-adults during the wet season and adults, and juveniles during the dry season. In contrast, lion preferred adult prey irrespective of season, with sub-adults, juveniles, and neonates killed relative to their abundance. This highlights that traditional, crude prey preference models do not adequately account for demographic-specific prey preference and thus may mask the level of prey use and potential preferences for different demographic classes. This is particularly important for smaller predators, like cheetah, where prey selection is largely confined to juveniles, meaning that prey availability would vary seasonally, and carrying capacity models would need to be revised in terms of the available prey biomass. Therefore, carrying capacity estimates calculated using the crude prey preference models are likely less useful for smaller predators like cheetah, but may be adequate for larger predators like lion.