Effects of mesopredators and prescribed fire on hispid cotton rat survival and cause‐specific mortality

Abstract

Control of mid‐sized mammalian predators (hereafter, mesopredators) is sometimes advocated in an attempt to reduce their impact on wildlife populations, particularly economically important (i.e., game) or endangered species. However, mesopredators may play a role in regulating small mammal populations; thus, lethal control of mesopredators may have unintended consequences. The hispid cotton rat (Sigmodon hispidus; hereafter, cotton rat) is one of the most common small mammals in the southeastern United States and is an important prey species for several of the region's predators. Within fire‐maintained communities, such as the longleaf pine (Pinus palustris) forests of the Coastal Plain, cotton rat populations dramatically, yet temporarily, decline following prescribed fire. To evaluate the effects of mesopredator removal on cotton rat survival and cause‐specific mortality, we conducted a large‐scale mesopredator exclusion experiment that incorporated a prescribed fire during the winter of study. Between 18 May 2006 and 20 June 2007, we used radio‐telemetry to monitor 252 cotton rats (131 in exclosures and 121 in controls) and documented 184 mortalities. During the 37‐week period of monitoring prior to the prescribed fire event, weekly survival of cotton rats was greater in mesopredator exclusion plots. During the 19 weeks following the prescribed fire, there were no differences in weekly survival relative to mesopredator treatment, but fire caused a short‐term reduction in weekly survival within both exclosures and controls. Of 36 cotton rats monitored on the date of prescribed fire, 18 were depredated within 1 month, 4 emigrated, and 5 were killed by the fire event. Overall, raptors preyed on cotton rats more in exclosures than in controls, but evidence for compensatory predation (raptor‐caused morality greater in exclosures than in controls although survival rates were similar between treatments) only occurred following the prescribed fire event. Our results suggest that managing mesopredators may result in a temporary increase in cotton rat survival, but dormant season prescribed fire removes this effect until well into the following growing season. © 2011 The Wildlife Society.

Multiple threats, or multiplying the threats? Interactions between invasive predators and other ecological disturbances

“…That is, although the invasive predator's population density may remain stable, there is a shift in behaviour such that native fauna are more likely to be depredated when invasive predators co-occur with the threat. For example, predation rates of hispid cotton rats Sigmodon hispidus increased following prescribed fire in Georgia, USA (Conner et al, 2011). This is a 'functional' impact of invasive predators, as their impact on native prey populations is independent of their population density (Didham et al, 2007).…”

Feeling the pressure at home: Predator activity at the burrow entrance of an endangered arid‐zone skink

“…However, these two threatening processes are often studied independently rather than as drivers that interact synergistically; few studies have focused on their possible interactions, and indirect effects on species declines that may occur as a result of these interactions (Hobbs 2001;Didham et al 2005Didham et al , 2007Brook et al 2008;Chalfoun & Martin 2009;Conner et al 2011;McGregor et al 2014;Hradsky et al 2017).…”

“…Variability in vegetation structure influences the outcome of predator-prey interactions because predation risk and hunting success can be affected by attributes of the habitat occupied by both predator and prey (Moreno et al 1996;Janssen et al 2007;Chalfoun & Martin 2009;Conner et al 2011;McDonald et al 2016;Hradsky et al 2017). For example an experiment investigating the short-term effects of a prescribed fire on the red fox (Vulpes vulpes) and feral cat (Felis catus) and their native mammalian prey in southeastern Australia found that under prefire conditions invasive predators were more likely to occur at sites with an open understory, whereas most small-and medium-sized native mammals were positively associated with understory cover.…”

Adult bobcat (Lynx rufus) habitat selection in a longleaf pine savanna

“…We expected bobcats to select for areas with lower basal areas managed by frequent fire that contained an abundance of understory vegetation. Selection of young pines in the Mississippi studies was primarily due to relative abundance of small mammals in young pines (Conner 1991, Conner et al 1992. Many young pines in our study area contained little herbaceous vegetation and few small mammals (Golley et al 1965, Schnell 1968, McMurry et al 1994, Masters et al 1998, which may explain why bobcats were farther from young pines.…”

“…In addition, frequent use of prescribed fire in longleaf pine forests increases understory plant species richness, diversity, and evenness (Brockway and Lewis 1997), which may influence where bobcats search for prey items. Small mammals (e.g., cotton rats [Sigmodon hispidus], Conner et al 2011, Morris et al 2011 are commonly exposed to predation from bobcats and other predators following a fire event due to reductions in herbaceous cover. Our results may also be due to the scale of fire relative to bobcat home ranges.…”