Hunting Mortality Research Articles

Methodological advances

The study of population dynamics has long depended on methodological progress. Among many striking examples, continuous time models for populations structured in age (Sharpe & Lotka, 1911) were made possible by progress in the mathematics of integral equations. Therefore the relationship between population ecology and mathematical and statistical modelling in the broad sense raises a challenge in interdisciplinary research. After the impetus given in particular by Seber (1982), the regular biennial EURING conferences became a major vehicle to achieve this goal. It is thus not surprising that EURING 2003 included a session entitled “Methodological advances”. Even if at risk of heterogeneity in the topics covered and of overlap with other sessions, such a session was a logical way of ensuring that recent and exciting new developments were made available for discussion, further development by biometricians and use by population biologists. The topics covered included several to which full sessions were devoted at EURING 2000 (Anderson, 2001) such as: individual covariates, Bayesian methods, and multi–state models. Some other topics (heterogeneity models, exploited populations and integrated modelling) had been addressed by contributed talks or posters. Their presence among “methodological advances”, as well as in other sessions of EURING 2003, was intended as a response to their rapid development and potential relevance to biological questions. We briefly review all talks here, including those not published in the proceedings. In the plenary talk, Pradel et al. (in prep.) developed GOF tests for multi–state models. Until recently, the only goodness–of–fit procedures for multistate models were ad hoc, and non optimal, involving use of standard tests for single state models (Lebreton & Pradel, 2002). Pradel et al. (2003) proposed a general approach based in particular on mixtures of multinomial distributions. Pradel et al. (in prep.) showed how to decompose tests into interpretable components as proposed by Pollock et al. (1985) for the Cormack–Jolly–Seber model. Pledger et al. (in prep.) went on in their thorough exploration of models with heterogeneity of capture (Pledger & Schwarz, 2002; Pledger et al., 2003), by considering the use of finite mixture models for the robust design. Given the level of details in demographic traits presently addressed by capture–recapture, the problem of heterogeneity, once apparently settled by fairly reassuring messages (Carothers, 1973, 1979), is becoming again a central issue, with potential disastrous consequences if improperly handled. Heterogeneity models, that bear also a relationship to “multi–event models” (Pradel, in press), will thus certainly be increasingly useful. Pollock, Norris, and Pledger (in prep.) reviewed the capture–recapture models as applied to community data (Boulinier et al., 1998) and developed general removal and capture–recapture models when multiple species are sampled to estimate community parameters. Because of unequal delectability between species, these approaches bear a clear relationship to heterogeneity models, which will be more and more a reference for comparative studies of communities and “macroecology” (Gaston & Blackburn, 2000). Bonner & Schwarz (2004) proposed a capture–recapture model with continuous individual covariates changing over time more fully developed in Bonner & Schwarz (2004). The difficulty here is to set up a sub–model predicting the covariate value when an individual is not captured. While multi–state models permit an ad hoc treatment by categorizing the covariate, Bonner and Schwarz bring a sound answer by considering the covariate obeys a Markov chain with continuous state–space. Otis & White (2004) presented a thorough, simulation–based, investigation of two approaches used to test the contrasting hypotheses of additive and compensatory hunting mortality based on band recovery data. The two approaches are the usual ultra–structural model and a new one based on a random effects model. Thispaper can be viewed as part of a revival of studies of the dynamics of exploited populations, in the broad sense, including the study of man–induced mortality in the framework of conservation biology (Lebreton, in press). This revival is a direct consequence of the increasing impact of man on the biosphere and of continuing methodological progress (Ferson & Burgman, 2000). The use of random effects models (see also Schaub & Lebreton, 2004) directly builds upon the seminal work by Anderson and Burnham (1976). Stauffer presented a Winbugs implementation of the Cormack–Jolly–Seber model that complemented other presentations in the conference and the short course. Finally, Morgan, Besbeas, Thomas, Buckland, Harwood,Duck and Pomery, proposed a thorough and timely review of integrated modelling, i.e., in our context, of models considering simultaneously capture–recapture demographic information and census information. These methods were covered in other sessions, in relation to Bayesian methodology. Integrated modelling appears indeed to be the logical way of combining all pieces of information arising from integrated monitoring, and as one of the great methodological challenges for our community in the years to come (Besbeas et al., 2002).

Of reindeer and man, modern and Neanderthal: A creation story founded on a historic perspective on how to conserve wildlife, woodland caribou in particular

A review of successful systems of wildlife conservation, the North American included, suggests that broad public support and determined effort by volunteers is essential for wildlife conservation. Since North American wildlife conservation is the only large-scale system of sustainable natural resource use, and exemplifies the great economic and cultural benefits of a renewable resource held in common, its lessons may be profitably applied to Rangifer conservation. Animals that have value are surrounded by myths that tell of their relationship to humans. In our Anglo-American culture reindeer and caribou are rather deficient in this respect. However, reindeer feature prominently in the rise of modern humans and the demise of Neanderthal man early in the Upper Paleolithic. The colonization by humans of the periglacial environments during the last glaciation depended on the rich periglacial megafauna, Rangifer included. Archeological sites of the European Upper Paleolithic show that reindeer were the most important food source. The Upper Paleolithic, characterized by exceptional physical development and health of people, as well as by the first flowering of art, extended from Spain to Crimea with surprisingly little cultural change for some 25 000 years. While the cave paintings express an infatuation with dangerous game (woolly mammoth, woolly rhino, steppe wisent, giant deer, cave lions, bears etc), the archeological sites indicate that reindeer was the staple food. Reindeer play a minor role in cave art. Neither this art, nor archeological sites, show any evidence of warfare. It is hypothesized that during a mid-glacial interstadial modern people entered Europe having developed a highly successful system of hunting reindeer using interception based on the discovery of chronologic time. This led to a first flowering of culture based on a rich economy, but also to additional hunting mortality of the periglacial mega-herbivores that Neanderthal people depended on. That would explain the slow decline into extinction of the previously invincible Neanderthal people. Therefore, modern humans owe much of what they are to reindeer. We need to reciprocate. What is urgently required is a foundation formed by volunteers for the conservation of caribou, similar to the Rocky Mountain Elk Foundation, focusing on the severely endangered wood¬land caribou.

Changes in survival rates and population dynamics of greater snow geese over a 30‐year period: implications for hunting regulations

SummaryIn recent decades, the populations of several goose species have increased dramatically and are severely impacting on their habitat. We examined the relative contribution of reproduction and mortality to changes in the dynamics of the entire North American population of greater snow geeseAnser caerulescens atlanticusfrom 1970 to 1998.The total population increased 10‐fold over this period, with two phases of rapid population growth in 1970–74 and 1984–98 separated by an intervening period of stagnation. The reproductive rate was estimated from age ratios in the autumn, survival from ring recoveries, and harvest rates from hunter surveys.Variations in population growth could not be explained by changes in reproduction, which was similar across the three periods (overall mean 26 ± 3% young in the autumn flock) with no evidence of density‐dependence.Adult survival did not differ between the two periods of rapid population growth (0·84 ± 0·04 during 1970–74 vs. 0·80 ± 0·04 during 1990–96), thus providing no evidence of density‐dependence effects either. The survival rates of young could only be estimated during 1990–96, when they varied greatly (mean 0·36 ± 0·12, annual range 0·11–0·48).Adult harvest rates were much higher during the period of no population growth (0·11 ± 0·01%) than before (0·04 ± 0·01%) or after (0·06 ± 0·01%). The increased harvest starting in 1975 was due to the re‐opening of the US hunting season. Thus, reduced survival due to increased hunting mortality apparently caused the stagnation of growth between 1975 and 1983.We conclude that hunting mortality has had the most impact on recent population dynamics in the greater snow goose and, in the absence of density‐dependent effects, hunting could be used to limit the growth of this population.

Age-specific moose (Alces alces) mortality in apredator-free environment: Evidence for senescence in females

We tested whether the ungulate moose (Alces alces) showed senescence in survival. Senescence, i.e., a progressive deterioration with age, may be obscured by multiple mortality causes in a wild population. Thus, we followed radio-marked individuals of known age to separate different mortality causes in adult moose. The risk of dying of causes not linked to humans increased with age. For females, the increase in natural mortality was first observable after age 10. Tooth wear was significantly related to age for both sexes, but was stronger for males. It suggests that males would experience senescence in survival earlier than females in a non-hunted population. The senescence in mortality observed for female moose may be a result of delayed cost of reproduction acting in concert with tooth wear due to a reduced ability to process food. We also found an increase in hunting mortality with age for both sexes, with males facing a higher risk of dying than females. The age-related hunting mortality may be a result of selectivity by the human predator, or a change in moose behaviour with age.

Survival of Postfledging Mallards in Northcentral Minnesota

Effective, economical management of waterfowl populations requires an understanding of age-, sex-, and cause-specific forces of mortality. We used radiotelemetry to estimate survival rates of immature mallards (Anas platyrhynchos) from fledging to autumn migration in northcentral Minnesota We monitored 48 females and 42 males during 1972-74 and observed:31 deaths during 2,984 exposure-days We attributed 7 deaths to predation and 24 to hunting. Survival rates were 0.86 (SE = 0.047) or the postfledging-prehuntin period, 0.29 (SE = 0.107) from the onset of hunting to migration, and (SE = 0.094) for both periods combined. Natural mortality of fledged young had a negligible effect on recruitment to migration Reducing natural mortality of fledged juvenile mallards would not have been a feasible means of increasing recruitment. Management strategies that increased nest success, increased brood survival, or decreased hunting mortality would more likely have produced meaningful gams in recruitment and are worthy subjects for continuing study. In northcentral Minnesota, changes in waterfowl habitats, predator populations, and hunting pressure have probably not changed the relative importance of hunting and nonhunting mortality to fledged juvenile mallards since our data were collected.

Culling of lynxes Lynx lynx related to livestock predation in a heterogeneous landscape

Lynx Lynx lynx hunting in Norway is regulated through regional quotas according to the magnitude of predation on semi‐domesticated reindeer Rangifer tarandus and domestic sheep Oves aries. Lynxes and semi‐domesticated reindeer were studied using telemetry in an area in Nord‐Trøndelag County, Norway, with high lynx predation on reindeer and domestic sheep and a high hunting pressure on lynxes. The probability of an ungulate killed by lynxes being livestock as opposed to a roe deer (the only alternative wild ungulate) increased with increasing distance from fields (P < 0.0001) and roads (P < 0.0001). Hunting was the only mortality cause found for radiocollared lynxes. The culling of lynxes was biased towards the vicinity of roads and cultivated fields compared with the general distribution of radiocollared lynxes (P < 0.001) and radio‐collared semi‐domesticated reindeer killed by lynxes (P < 0.001). Because of the easy location in rural areas due to the well‐developed road system, lynxes suffered the highest hunting mortality in habitats where the proportion of livestock in the diet was lowest, whereas lynxes inhabiting alpine areas more than 3 km from the nearest road escaped hunting. The hunters' preference for hunting lynxes near roads leads to a risk of selective reduction in regions and habitats where lynxes do little harm, whereas numbers in remote areas with high predation on livestock may remain unaltered.

A Stochastic Dynamic Programming Model for the Management of the Saiga Antelope

A stochastic dynamic programming model for the optimal management of the saiga antelope is presented. The optimal hunting mortality rate and proportion of adult males in the harvest are found as functions of the size and structure of the saiga population before hunting. The effects of stochastic climatic variation on the population are taken into account in this model. It is shown that key assumptions must be made about the effects of the breeding sex ratio on female fecundity, and about whether poaching is occurring. If incorrect assumptions are made about either of these factors, the calculated optimal strategy can become severely suboptimal. A simple suboptimal decision rule that takes the population size and structure into account is shown to be more able to buffer against these factors than the optimal strategy, which has proved too complicated for analytical solution. The model predictions are robust to parameter changes.

A STOCHASTIC DYNAMIC PROGRAMMING MODEL FOR THE MANAGEMENT OF THE SAIGA ANTELOPE

A stochastic dynamic programming model for the optimal management of the saiga antelope is presented. The optimal hunting mortality rate and proportion of adult males in the harvest are found as functions of the size and structure of the saiga population before hunting. The effects of stochastic climatic variation on the population are taken into account in this model. It is shown that key assumptions must be made about the effects of the breeding sex ratio on female fecundity, and about whether poaching is occurring. If incorrect assumptions are made about either of these factors, the calculated optimal strategy can become severely suboptimal. A simple suboptimal decision rule that takes the population size and structure into account is shown to be more able to buffer against these factors than the optimal strategy, which has proved too complicated for analytical solution. The model predictions are robust to parameter changes.

Use of Solicited Bands and Separation of Hunting and Natural Mortality: A Comment

We previously presented (Conroy 1985, Conroy et al. 1989) models for analysis of band recovery data stratified into those voluntarily reported and those obtained by solicitation, similar to models described by Pollock et al. (1994). We discuss differences between the 2 modeling approaches and suggest designs and analyses involving overlapping samples of standard and reward bands to enable adjustment for temporal and geographic variation in reporting and solicitation rates.

Band Return Models: Use of Solicited Bands and Separation of Hunting and Natural Mortality

The Brownie et al. (1985) band return models have been widely used to estimate survival and recovery rates for hunted species, especially migratory waterfowl. We developed a generalization of the Brownie models that allowed incorporation of solicited and reported bands into one analysis. This is an important addition to banding model literature, which has ignored solicited bands in the model formulation. Furthermore, if a reporting rate estimate is available from, for example, a reward banding study and a retrieval rate (1 − crippling loss rate) from a hunter questionnaire survey, we show that it is possible to estimate harvest rate, kill rate, and hence natural mortality rate in the presence of hunting

Survival and Hunting Mortality of Pacific Black Ducks and Grey Teal

To examine the importance of hunting mortality in the population dynamics of waterfowl in southwestern Australia, we estimated survival and recovery rates of 19,523 Pacific black ducks (Anas super-ciliosa) and 2,487 grey teal (A. gibberifrons) banded in 1968-76 and recovered by 1978. Both species showed strong evidence of year-to-year variation in survival rates, which averaged 63 +/- 4(SE)% and 56 +/- 6% for adult and young Pacific black ducks, respectively, and 55 +/-17% for adult grey teal. First-year recovery rates indicated the average annual hunting mortality over 6 years for Pacific black ducks and grey teal exposed to heavy hunting pressure was 23 +/-2% and 17 +/-2%, respectively. Hunting mortality was 9% in 1 year for Pacific black ducks exposed to light hunting. Estimates of mortality rate on opening day of hunting seasons at a site of intense hunting varied between 7 and 20% for Pacific black ducks and 5 and 16% for grey teal. In an intensively hunted waterfowl population in southwestern Australia, nearly 60% of all mortality of Pacific black ducks and 40% of grey teal mortality resulted from hunting. Hunting probably caused <25% of mortality in most parts of southwestern Australia, however, and there was no evidence of hunting reducing survival rates.

Effect of Hunting on Annual Survival of Canada Geese in Utah

The competing hypotheses of additive and compensatory hunting mortality have not been investigated in Canada geese (Branta canadensis moffitti). Thus, I analyzed band-recovery data consisting of 37,942 bands and 10,451 recoveries from Canada geese banded in Utah during 1952-84. Investigations of the hypotheses of additive and compensatory mortality were conducted on the basis of response of survival rates to variations in harvest regulations, correlation of survival rates with recovery rates, and linear relationships between survival rates and kill rates. Survival rates showed weak relationships to variation in season length, were found to be negatively correlated with recovery rates (adult P=0.016), and showed weak evidence of linearity in relation to kill rates. Whether these relationships are manifestations of additive mortality, or compensatory mortality operating above the threshold point, cannot be determined

Population Dynamics of Bison in the Henry Mountains, Utah

We assessed structure, survival, productivity, and growth of a Bison bison population in southern Utah during 7 years. Consistently female-biased sex ratios resulted from male-biased hunting mortality and possibly from lower survival of young males. Survival, excluding hunting mortality, was high for all animals and probably was facilitated by a lack of predators and by prolonged parental care of young. Productivity was correlated nonlinearly with precipitation and was lower than in other herds, possibly because of relatively sparse forage. The herd has been increasing exponentially since establishment in the early 1940's, despite annual hunts, low forage production, and possible competition with domestic cattle. Increase has been particularly rapid during an extraordinary series of relatively wet years since the drought of 1977, raising the question of whether the herd has exceeded long-term carrying capacity.

Sex-Specific Hunting Mortality of Greater Snow Geese along Firing Lines in Quebec

Sex-Specific Hunting Mortality of Greater Snow Geese along Firing Lines in Quebec

Compte rendu ornithologique camarguais pour les années 1980 et 1981

Compte rendu ornithologique camarguais pour les années 1980 et 1981