Culling Versus Density Effects in Management of a Deer Population

Abstract

: Wildlife managers often manipulate hunting regulations to control deer populations. However, few empirical studies have examined the level of hunting effort (hunter‐days) required to limit population growth and demographic effects through harvesting of females. Moreover, the relative importance of density effects on population growth has not been quantified. We reconstructed a sika deer [Cervus nippon] population over a period of 12 years (1990–2001) using age‐ and sex‐specific harvest data. Using cohort analysis, we analyzed population dynamics, focusing on 1) the relationship between hunting effort and hunting‐induced mortality rate, 2) relative contributions of hunting mortality and recruitment of yearlings to annual changes in population growth rate, and 3) annual variation in recruitment rate. Population size increased until 1998 and declined thereafter. The population growth rate changed more in response to annual changes in recruitment rate than hunting mortality rate. Temporal variation in recruitment rate was not controlled by birth rate alone; direct density dependence, intensities of hunting mortality for fawns, and for females (≥2 yr of age), which accounted for the fawn survival rate, were required as factors to explain temporal variation. Density effects on the recruitment rate were not strong enough to regulate the population within the study period; high hunting mortality, with intensive female harvesting, was necessary to prevent population growth. Hunting effort was a good predictor of the hunting mortality rate, and female harvest had a negative effect on the recruitment rate through fawn survival. We suggest that >3,500 hunter‐days and prioritization of female harvesting are required to prevent increases in this deer population.

Density-dependent nest predation in waterfowl: the relative importance of nest density versus nest dispersion

“…Understanding density-dependent processes is important for the conservation of exploited, endangered, or heavilymanaged species (Hixon and Carr 1997;Ueno et al 2010). In one such group, North American waterfowl, density dependence in population growth has been demonstrated consistently at large spatial and temporal scales (Vickery and Nudds 1984;Viljugrein et al 2005;Saether et al 2008;Murray et al 2010), yet the underlying processes that produce these patterns remain elusive.…”

Applying typology analyses to management issues: Deer harvest and declining hunter numbers

“…Hunters form a broadly mixed group with diverse behaviors, and some hunters are less effective than others for meeting quota objectives (Lebel et al ). For example, the most effective way to reduce ungulate populations is to increase the harvest of adult females (e.g., Ueno et al , Milner et al , Boulanger et al ), yet some hunters do not pursue females for nonobjective reasons. Such established beliefs make implementing new harvesting regimes difficult (Finch and Baxter , Cornicelli and Grund ).…”

Anthropogenic Influences on Conservation Values of White Rhinoceros

“…Indeed, managers typically removed relatively more sub-adult females in a particular year compared to what was available in the population at the time. Such selective removal may result in demographic cascades [30] and contribute to the large population size effect associated with management related removals. Selective removal may also impose evolutionary constraints [53] and have indirect long-term effects on genetic integrity of the population.…”

“…Such size selection by poachers is well known for elephants [54] and ultimately induces structural as well as demographic changes that lead to critical thresholds when populations collapse rapidly [30]. Poaching may thus pose a significant threat to population persistence when populations decline to threshold levels.…”

“…Source-sink dynamics may lead to local instability, but regional stability [29], a feature desirable if conservationists wish to maintain persistent biodiversity. However, such strategies may lead to drifts in age structures that may carry long term consequences for the population specifically if removal of excess is selective [30]. These concerns are pertinent for the white rhino management model that Kruger managers adhere too.…”