Survival of translocated sharp-tailed grouse: temporal threshold and age effects

Abstract

Context. The Columbian sharp-tailed grouse (Tympanuchus phasianellus columbianus) is a subspecies of conservation concern in the western United States, currently occupying 10% of its historic range. Land and management agencies are employing translocation techniques to restore Columbian sharp-tailed grouse (CSTG) populations. However, establishing self-sustaining populations by translocating grouse often is unsuccessful, owing, in part, to low survivorship of translocated grouse following release.Aims. We measured and modelled patterns of CSTG mortality for 150 days following translocation into historic range, to better understand patterns and causes of success or failure in conservation efforts to re-establish grouse populations.Methods. We conducted two independent multi-year translocations and evaluated individual and temporal factors associated with CSTG survival up to 150 days following their release. Both translocations were reintroduction attempts in Nevada, USA, to establish viable populations of CSTG into their historic range.Key results. We observed a clear temporal threshold in survival probability, with CSTG mortality substantially higher during the first 50 days following release than during the subsequent 100 days. Additionally, translocated yearling grouse exhibited higher overall survival (0.669 AE 0.062) than did adults (0.420 AE 0.052) across the 150-day period and higher survival than adults both before and after the 50-day temporal threshold.Conclusions. Translocated CSTG are especially vulnerable to mortality for 50 days following release, whereas translocated yearling grouse are more resistant to mortality than are adult grouse. On the basis of the likelihood of survival, yearling CSTG are better candidates for population restoration through translocation than are adult grouse.Implications. Management actions that ameliorate mortality factors for 50 days following translocation and translocations that employ yearling grouse will increase the likelihood of population establishment.

Optimizing release strategies: a stepping‐stone approach to reintroduction

“…This can be particularly true for species that are slow to Figure 5 Event tree diagram describing the probability a captive marmot pup (Age 0) alive at the end of its first year survived to become a prime breeding-age adult (PBA) at Strathcona (P PBA ; mode and 95% credible interval). However, individuals that are released at older ages can be disadvantaged if they are less adaptable and consequently have high pre-breeding mortality (Mathews, Coates & Delehanty, 2016), or experience release effects that delay breeding (Saltz & Rubenstein, 1995). Locations include Mt Washington (MW), Strathcona (ST), and captivity (CA).…”

“…reach reproductive maturity and breed infrequently. However, individuals that are released at older ages can be disadvantaged if they are less adaptable and consequently have high pre-breeding mortality (Mathews, Coates & Delehanty, 2016), or experience release effects that delay breeding (Saltz & Rubenstein, 1995). For Vancouver Island marmots, releasing captive-bred adults directly into Strathcona appears to be ineffective regardless of release method, and may be considered unethical by some (Harrington et al, 2013).…”

A Population Viability Analysis for Sharp-Tailed Grouse to Inform Reintroductions

“…We set annual survival to 0.50 based on the mean value from a review of 10 published studies (Table 2). However, annual survival of translocated female sharptailed grouse was reduced by 50% in the first year posttranslocation (Mathews et al 2016). Based on these estimates, we set annual survival of translocated birds at 0.25 for the first year.…”

“…Three scenarios modeled different translocation techniques. First, we modeled translocating just yearlings (scenario A) based on reported 59% higher survival (0.67 vs. 0.42) of yearling vs. adult translocated sharp-tailed grouse (Mathews et al 2016). Second, we modeled the effects of supplementation on population persistence by supplementing 10 grouse annually for the first 5 y at K values of 500 and 1,000 for the baseline (scenario Ba) and juvenile (scenario Bb) translocation scenarios.…”

Conservation translocations of Hawaiian monk seals: accounting for variability in body condition improves evaluation of translocation efficacy

“…In making such comparisons among treatment groups, however, one assumes that the groups consist of otherwise equivalent individuals. A variety of factors such as the age, mass, sex, behavioral traits, and experience of individuals can influence post-translocation survival (Bremner-Harrison, Prodohl, & Elwood, 2004;Frair et al, 2007;Attum et al, 2010;Cabezas, Calvete, & Moreno, 2011;Day, Westover, & McMillan, 2013;Mathews, Coates, & Delehanty, 2016;West et al, 2018;Hare et al, 2019). Failing to account for such factors may render comparison of treatment and control groups invalid.…”