Experimental manipulation of perceived predation risk alters survival, cause of death, and demographic patterns in juvenile snowshoe hares

Abstract

Perceived predation risk alters prey behaviour and physiology, but few studies have examined downstream consequences on prey demography in wild populations. Perceived predation risk could alter adult reproductive performance via reduced investment in offspring quality and post-birth care. We manipulated perceived predation risk in snowshoe hare ( Lepus americanus Erxleben, 1777) by exposing pregnant mothers to chases by a domestic dog ( Canis familiaris Linnaeus, 1758). Litter size was comparable between risk-augmented and control groups, but treated females had more stillbirths and gave birth to leverets of lower body condition. Leverets from risk-augmented females had 88% higher 40-day mortality rate. Maternally preventable causes of death like starvation or predation by red squirrel ( Tamiasciurus hudsonicus (Erxleben, 1777)) caused this difference, particularly during the nursing period. Risk-augmented mothers were always more active than controls, but the difference was greatest during the nursing period. We found that perceived predation risk reduces maternal productivity pre- and post-partum, implying downstream consequences to populations. Because our treatment ended before parturition, we can link offspring performance such as survival and behaviour specifically to maternal life-history trade-offs, which has not been shown in a wild mammal.