Population dynamics of reintroduced Gunnison's Prairie dogs in the southern portion of their range

Abstract

Burrowing, herbivorous mammals play important roles as ecosystem engineers and keystone species of grassland ecosystems around the world, but populations of many species have declined dramatically because of myriad threats from human activities. Prairie dogs (Cynomys spp.) play important roles in shaping the central grasslands of North America, and have declined by about 98% across their range, with consequent losses in associated species and grassland habitat. This has prompted much interest in restoring their populations to protected areas. Managers lack a clear understanding of the long‐term success of reintroductions, however, and how success may vary across different species of prairie dogs and their widespread geographic ranges. We reintroduced over 1,000 Gunnison's prairie dogs (C. gunnisoni) to a semi‐arid grassland ecosystem in the southern portion of their range in central New Mexico, USA, and used standard capture–recapture methods to study their population dynamics over a period of 8 years. Mean adult survival was 27% over the course of the study, with precipitation identified as the primary driver of survival. Estimated survival was below 12% during severe drought periods and during the first few years following initial reintroduction, the latter likely because of high predation. Consequently, multiple releases of animals were required to prevent extirpation, and the long‐term sustainability of this population remains questionable. Over the 8 years of our study, our site experienced 4 severe droughts during spring, the key period for prairie dog mating, pregnancy, and lactation. Production of offspring at the site was low, likely because of the dry and variable conditions that occurred. We show that prairie dog restoration in semi‐arid grassland environments that are typical of the lower elevations and southern extent of their range may not succeed in producing viable colonies, and that dedicated management for multiple years is needed to counteract periods of slow or negative population growth. Our findings underscore the importance of maintaining and expanding existing colonies wherever possible in these more arid regions, and suggest that reintroductions should be treated as a secondary management strategy. Our work also reveals the high vulnerability of prairie dog population extinction due to drought, which has important implications for Gunnison's prairie dog conservation under a warming and drying climate. © 2014 The Wildlife Society.

Reintroducing a keystone burrowing rodent to restore an arid North American grassland: challenges and successes

“…Recruitment only began to increase once the drought receded in winter 2013–2014. Drought periods have been found to limit reproductive success in other prairie dog populations (Facka et al ; Davidson et al ; Hayes et al ). Furthermore, several previous studies have suggested that prairie dog recruitment (and to a lesser extent, survival) is most limited by winter–spring precipitation, which triggers spring green‐up of vegetation that provides critical forage resources during the energetically‐demanding periods of mating, pregnancy, and lactation (Hoogland ; Hayes et al ).…”

“…20% chance of surviving the first month following release (averaged across all release events), which is lower than reported in other studies of translocated black‐tailed prairie dogs during the first few months postrelease (40–80%; Bly‐Honness et al ; Dullum et al ; Long et al ). Low 1‐month postrelease survival is likely due in part to movement off‐site and predation (Long et al ; Shier ; Davidson et al ). For example, we radio‐collared 11 reintroduced prairie dogs (unpublished data) and found that several individuals moved far from our release sites (with one confirmed mortality via predation), so some of the losses during the first month were due to animals leaving the relocation site, and probably resulted in mortality.…”

“…Prairie dog occupied habitat and prairie dog numbers continue to be lost due to deliberate persecution (e.g. poisoning and shooting) (Miller et al ; Bergstrom et al ), in addition to introduced exotic disease (sylvatic plague; (Cully et al ; Eads & Biggins ), habitat loss (Ceballos et al ), and, increasingly, climate change (Ceballos et al ; Davidson et al ; Eads & Biggins ; Eads & Hoogland ).…”

“…), similar to the rippling effects that other keystone species have had when reintroduced, such as beavers ( Castor Canadensis ), sea otters ( Enhydra lutris ), and wolves ( Canis lupus ) (Hastings et al ; Gibson & Olden ; Ripple et al ). Therefore, understanding how to successfully restore and maintain prairie dog populations across their range, and if/how reintroduction efforts help to restore their functional role, is important for grassland conservation and management (Davidson et al ). Reintroductions of prairie dogs often entail translocating them from areas where they are in conflict with humans to wildlife refuges (e.g.…”

“…Considerable research has been conducted to determine successful methodologies for reestablishing prairie dogs (especially C. ludovicianus ), which involves releasing them into pre‐existing burrows or constructed artificial burrow systems (Long et al ). Despite numerous reintroduction efforts occurring across their ranges over the last two decades, the long‐term (decadal) success of reintroductions and how success varies across different parts of their geographic range remains limited (Facka et al ; Davidson et al ). Such information is needed in the context of climate change, especially in the southern portion of their ranges that is projected to become increasingly warmer and drier (Seager et al ; Gutzler & Robbins ).…”