Individual heterogeneity and effects of harvest on greater sage‐grouse populations

Caudill, Danny; Guttery, Michael R.; Terhune, Theron M.; Martin, James A.; Caudill, Gretchen; Dahlgren, David K.; Messmer, Terry A.

doi:10.1002/jwmg.21241

Cited by 8 publications

(10 citation statements)

References 117 publications

(214 reference statements)

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“…Our findings provide an additional consideration regarding the potential for harvest to reduce population size through reduced survival rates. The likely presence of heterogeneous survival via variation in body condition allows for possible harvest compensation without requiring density dependence (Lebreton , Caudill et al ). Therefore, disproportionate harvest of poorer‐conditioned lesser snow and Ross's geese in decoy‐hunting situations may serve as an additional challenge against any realized effects of harvest.…”

Section: Management Implicationsmentioning

confidence: 99%

“…Support for density dependence as a mechanism for compensatory harvest, particularly in ducks, has been equivocal (Pöysä et al , Viljugrein et al , Murray et al , Sedinger and Herzog ), but it is evident that density‐dependent pressures must be substantial to affect adult survival rates (Bonenfant et al ). Nonetheless, individual variation in survival can serve as a mechanism for compensation and can have implications for effects of harvest on population change (Lebreton , Caudill et al ). Caudill et al () demonstrated that given some degree of additive harvest in a population comprised of groups with heterogeneous survival rates, disproportionate harvest of low‐quality individuals (i.e., those with lower survival and reproductive rates) will induce partial compensation.…”

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confidence: 99%

“…Nonetheless, individual variation in survival can serve as a mechanism for compensation and can have implications for effects of harvest on population change (Lebreton , Caudill et al ). Caudill et al () demonstrated that given some degree of additive harvest in a population comprised of groups with heterogeneous survival rates, disproportionate harvest of low‐quality individuals (i.e., those with lower survival and reproductive rates) will induce partial compensation. Therefore, even in the absence of density dependence and with substantial harvest rates, bias towards harvest of low‐quality individuals can reduce harvest effects on population reduction (Lebreton , Cooch et al ).…”

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confidence: 99%

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Condition Bias of Decoy‐Harvested Light Geese During the Conservation Order

2019

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Evidence that decoy harvest techniques primarily remove individuals of poorer body condition is well established in short‐lived duck species; however, there is limited support for condition bias in longer‐lived waterfowl species, such as geese, where decoy harvest is considered primarily additive because of their high natural survival rates. We evaluated support for the harvest condition bias hypothesis of 2 long‐lived waterfowl species, the lesser snow goose (Anser caerulescens caerulescens) and Ross's goose (Anser rossii). We used proximate analysis to quantify lipid and protein content of lesser snow and Ross's geese collected during the Light Goose Conservation Order (LGCO) in 2015 and 2016 during spring migration in Arkansas, Missouri, Nebraska, and South Dakota, USA. In each state, LGCO participants collected birds using traditional decoy techniques and we collected birds from the general population using jump‐shooting tactics. Total body lipid content in both lesser snow and Ross's geese varied with age, region of harvest, and harvest type (decoy or jump‐shooting). On average, adult lesser snow and Ross's geese harvested over decoys had 60 g and 41 g, respectively, fewer lipids than conspecifics collected using jump‐shooting. We observed lower lipid reserves in decoy‐shot geese in all 4 states sampled despite general gains in lipid reserves as migration chronology progressed. Our data support that the harvest condition bias extends to longer‐lived waterfowl species and during a life‐history event (spring migration) in which harvest is not normally observed. In the case of overabundant light geese, the disproportionate harvest of poorer‐conditioned lesser snow and Ross's geese may serve as an additional challenge against any realized effects of harvest to reduce the population, in addition to extremely low harvest rates. © 2019 The Wildlife Society.

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Section: Management Implicationsmentioning

confidence: 99%

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Condition Bias of Decoy‐Harvested Light Geese During the Conservation Order

2019

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“…For hunted species, the magnitude, timing, and demographic focus of harvest also has the potential to influence population dynamics. In particular, excessive or ill‐timed harvest can result in additive mortality or decreased recruitment (Burnham and Anderson 1984, Pollock et al 1989, Roland et al 2010, Blomberg 2015, Caudill et al 2017). In addition, differential harvest of individuals that exhibit heterogeneity in reproduction or survival has implications for the effect of harvest at the population level (Johnson et al 1984, Lebreton 2005, Lindberg et al 2013, Caudill et al 2017).…”

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confidence: 99%

Differential survival in the presence of spatially structured ptarmigan harvest suggests additive mortality

2022

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The effects of hunting on wildlife populations vary dramatically, depending on the timing and magnitude of harvest, and population-specific states and vital rates. We examined the hypothesis that spatially and seasonally concentrated harvest decreases annual survival probabilities of willow ptarmigan (Lagopus lagopus). We estimated survival of radio-marked willow ptarmigan at 2 categories of sites: those where ptarmigan were easily accessible and heavily hunted and those that were remote and received little or no hunting pressure in Alaska, USA. We predicted that seasonal survival estimates during the willow ptarmigan hunting season would be lower in access corridors than at remote sites and that this would result in lower annual survival unless subsequent seasonal compensatory mortality occurred. Consistent with our prediction, annual survival was higher at remote sites (adult males: 0.50, 95% credible interval [CrI] = 0.42-0.57; adult females: 0.36, 95% CrI = 0.26-0.46; juveniles: 0.39, 95% CrI = 0.29-0.50) than at accessible sites (adult males: 0.36, 95% CrI = 0.26-0.46; adult females: 0.23, 95% CrI = 0.12-0.32; juveniles: 0.25, 95% CrI = 0.13-0.37) for all demographic groups. Concentrated harvest occurred in accessible sites during the hunting season (Aug-Mar). During the post-breeding season (Aug-Nov), when willow ptarmigan were near their breeding sites and the hunting season was open, survival was higher for those from remote sites than for those from accessible sites when accounting for demographic group (adult male, adult female, juvenile). In contrast, during winter (Dec-Mar), when willow ptarmigan had

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“…Harvest effects manifest over time and most empirical studies that measure harvest are short‐term or do not explicitly consider harvest effects on vital rates. Harvest has typically been considered compensatory to natural mortality (Errington 1945, Allen 1947, Lack 1954, Bartmann et al 1992, Caudill et al 2017), but there are examples of harvest being partially additive (Williams et al 2004, Sandercock et al 2011). There is a knowledge gap about interactions between vital rates and harvest pressure under varying degrees of compensation (Roseberry 1979, Sandercock et al 2011, Péron 2013).…”

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Predation Management and Spatial Structure Moderate Extirpation Risk and Harvest of Northern Bobwhite

et al. 2020

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Density dependence, immigration, and emigration can considerably influence wildlife population demographics. Population models used to evaluate common actions like predator management and harvest in the absence of these processes may lead to poor management decisions. We built a novel population simulation model for the northern bobwhite (Colinus virginianus; bobwhite) that included implicit spatial structure (ingress and egress of individuals), density dependence, and harvest. We used 42 years of data (1970-2012) from a relatively stable population to create and validate the simulation model. We then used this simulation model to predict the effect of meso-mammal trap and removal, a management action that increases bobwhite fecundity, on population abundance, cumulative harvest through 50 years, and extirpation risk. We conducted a population sensitivity analysis to understand the implications of meso-mammal trap and removal to populations with varying vital rates. Incorporating ingress and egress of individuals and density dependence improved the understanding of bobwhite population dynamics and reduced the uncertainty about the efficacy of predator management across a range of environmental conditions. Increased number of immigration sources decreased extirpation risk and increased bobwhite abundance. A key outcome of our modeling process was that density-dependent processes did not fully compensate for harvest. Cumulative harvest through 50 years increased with increasing harvest rate but started to decline when harvest rate was >0.35 for populations with meso-mammal removal and 0.25-0.30 for populations without meso-mammal removal. Meso-mammal removal increased the harvest capacity of populations and produced greater harvest opportunity over time. Meso-mammal removal also buffered populations from extirpation risk resulting from too few immigration sources. Practitioners often ignore the contribution of immigration and emigration to local demographics or assume density-independent vital rates; however, recent literature reviews and our study indicate that these processes are important to the understanding of animal ecology and management. In the interest of the conservation of species that are hunted and at risk of extirpation in some geographies, predator management may increase hunter success and be a tool to reduce extirpation risk, although the degree of effectiveness likely varies geographically. This manuscript could serve as a framework for predicting the effects of management on bobwhite at the population level.

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Individual heterogeneity and effects of harvest on greater sage‐grouse populations

Cited by 8 publications

References 117 publications

Condition Bias of Decoy‐Harvested Light Geese During the Conservation Order

Condition Bias of Decoy‐Harvested Light Geese During the Conservation Order

Differential survival in the presence of spatially structured ptarmigan harvest suggests additive mortality

Predation Management and Spatial Structure Moderate Extirpation Risk and Harvest of Northern Bobwhite

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