Comparative Reproductive Ecology of Two Subspecies of Pacific Marten (Martes caurina) in California

Combined field and clinical methods clarify mortality causes and survival patterns of Pacific martens

“…During these periods, martens engage in sex-specific behaviors and reproductive processes that likely result in increased activity levels and energetic requirements for the respective sexes (Gittleman and Thompson 1988). Given female martens gestate for approximately 30 days and give birth in our study area from mid-April to mid-May (Delheimer et al 2021), the timing of increased mortality in our research directly corresponded to when females would have been actively pregnant or lactating. This finding corroborates previous reports that female marten survival is lowest from pregnancy to weaning (Wilk and Raphael 2018), when females appear to be particularly susceptible to predation (Bull and Heater 2001).…”

“…For example, male martens are larger‐bodied, have larger home ranges, and often exhibit higher energetic expenditures relative to female martens (Moriarty et al 2017, Martin et al 2020). Martens are often polygynandrous, where male martens typically attempt to mate with as many females as possible during a relatively brief mating period (i.e., Jul–Aug; Ruggiero and Henry 1993), whereas females incur the costs of pregnancy and kit‐rearing (i.e., Mar–Jul; Delheimer et al 2021). Though research suggests these aspects of animal behavior, physiology, and ecology may affect survival patterns (Promislow 1992, Mills 2007), inferences about the mechanisms influencing marten survival are often constrained by small sample sizes, variable estimates (Table 1), and uncertainty regarding sources of mortality.…”

“…North American martens (American marten [ Martes americana ], Pacific marten [ M. caurina ]) are small‐bodied (500–1,400 g; Nagorsen 1994), elusive mesocarnivores that exhibit some slow life‐history strategies. For example, female martens do not reach sexual maturity until the age of 2, typically produce small litters of 2–3 kits (Delheimer et al 2021), and may not reproduce every year after achieving sexual maturity. Unlike many other species exhibiting slow life histories, martens have relatively short lifespans in free‐ranging conditions (typically ≤ 5 yr), and, consequently, the survival of sub‐adult and adult martens influences population growth and persistence (Buskirk et al 2012).…”

Structural complexity characterizes fine‐scale forest conditions used by Pacific martens

“…We collected data at 2 study sites as part of broader research efforts investigating marten demography (Humboldt site; Delheimer et al 2021a) and marten space use (Lassen site; Moriarty et al 2015Moriarty et al , 2016b. Both study sites were in northern California and were located approximately 250 km apart (Figure 1).…”

Conservation of rare and cryptic species: Challenges of uncertainty and opportunities for progress

“…As an exercise in evaluating the status of a Humboldt marten population, we used data collected from 2012 to 2017 within the Northern Coastal California extant population area to simulate population growth rate ( λ ) with two demographic modeling approaches. Our first approach incorporated empirical Humboldt marten survival estimates derived from staggered entry Kaplan–Meier methods (Pollock et al, 1989) with fecundity estimates from the same population (Delheimer et al, 2021) into a deterministic stage–structured matrix demographic model that produced a range of growth rates (Caswell, 2001). Our second approach incorporated empirical Humboldt marten survival, derived from Cox proportional hazard methods (Cox, 1972), and fecundity estimates into a Monte Carlo sampling approach run for 5000 iterations that similarly produced a range of growth rates.…”