Wolf predation and snow cover as mortality factors in the ungulate community of the Bialowieża National Park, Poland

Abstract

Wolf-ungulate interactions were studied in the pristine deciduous and mixed forests of the Bialowieża National Park in 1985-1989. The study period included two severe and two mild winters. The community of ungulates inhabiting Bialowieża National Park consisted of red deer Cervus elaphus, 55% of all ungulates; wild boar Sus scrofa, 42%; and roe deer Capreolus capreolus, moose Alces alces, and European bison Bison bonasus, about 1% each. The average size of red deer groups increased from 2.7 (SD 2.35) in spring and summer to 6.9 (SD 6.84) in autumn and winter. In winter the group size of red deer was positively correlated with the depth of snow cover and negatively correlated with the mean daily temperature. Average group size of wild boar did not change significantly between seasons; it was 6.8 (SD 5.16) in spring and summer and 5.7 (SD 4.67) in autumn and winter. Analysis of 144 wolf scats showed that wolves preyed selectively on red deer. In October-April, Cervidae (mostly red deer) constituted 91% of biomass consumed by wolves, while wild boar made up only 8%. In May-September deer formed 77% of prey biomass, and the share of wild boar increased to 22%. In all seasons of the year wolves selected juveniles from deer and boar populations: 61% of red deer and 94% of wild boar of determined age recovered from wolves' scats were young <1 year old. Analysis of 117 carcasses of ungulates found in Bialowieża National Park showed that predation was the predominant mortality factor for red deer (40 killed, 10 dead from causes other than predation) and roe deer (4 killed, none dead). Wild boar suffered most from severe winter conditions (8 killed, 56 dead). The percentage of ungulates that had died from undernutrition and starvation in the total mortality was proportional to the severity of winter.

Prey selection and dietary response by wolves in a high-density multi-species ungulate community

“…The estimated body-weight ratio of prey to wolf in this study was lower than that observed in other study areas (Jędrzejewski et al 2002) or for other coursing predators, such as the African wild dog (Lycaon pictus) in South Africa (Radloff and Du Toit 2004). Furthermore, the ratio was lower than expected according to the general prey to predator mass relationships reported by Jędrzejewski (1998), andCarbone et al (1999).…”

“…Proportion in scats is expressed as relative number of prey. Significance, assessed by calculating the confidence intervals for p=0.01 and type of selection (positive sign, selection and negative sign, avoidance) were consistent throughout the period, except for roe deer juveniles and fallow deer adults in 1996 (α) Jędrzejewski et al 1992), we found that the percentage of wild boar in wolf diet was related to both the percentage of wild boar in the ungulate community (R 2 =0.515, n=13, p= 0.006) and the ratio between late-winter density of wild boar and red deer (R 2 =0.560, n=13, p=0.003). With respect to this picture, Casentinesi Forests represent an outlier, as wild boar use was double that expected by its abundance in the ungulate community.…”

“…Furthermore, the differences in the weight ratio between prey and predators can also play an important role. In Casentinesi Forests, the wild boar/wolf weight ratio for adult is half that in red deer (1.9 vs 3.7), while in Białowieża Forest the ratio is similar, 2.2 and 2.7, respectively (Jędrzejewska et al 1996;Jędrzejewska and Jędrzejewski 1998). Thus, the larger body size of adult boar, and consequently the greater possibility to successfully defend offspring from predation, might be another reason why wild boars are not often selected in northern regions.…”

“…Following preliminary results on wolf diet (Mattioli et al 1995), we extended our analysis of predator-prey relationships over an 11-year period. Firstly, we evaluated the response of wolves to wild ungulate density variations, by calculating both dietary response (sensu Jędrzejewska and Jędrzejewski 1998) and the strength of selection. We then applied a multiple-level selection analysis in order to better differentiate the effects of density, age and size on prey selection.…”

Sustainable monitoring of roe deer in public hunting areas in the Spanish Pyrenees

“…In our study, the recovery of roe deer carcasses suggested that mortality was highest in late winter and early spring, which is the time of year when snow cover can hinder the animal's movements and its ability to find food, leaving it vulnerable to starvation (Mysterud et al, 1997) and predation (Jȩdrzejewska et al, 1992). In addition, red fox is a potential predator of roe deer fawns (Panzacchi et al, 2008) and roe deer mortality is a subject worthy of further study.…”