E-mail deze pagina. Auteur: Hans Kruuk H. Uitgever: Cambridge University Press. Co-auteur: H.
Hunter and Hunted: Relationships between Carnivores and People | Commonwealth Honors College
Samenvatting Humans have mixed emotions concerning carnivores. We admire them as beautiful hunters, cosset them as pets, and use their pelts and other products in clothing, medicines and cosmetics. However, they are also responsible for killing us and our livestock, carry disease and compete with us for space and food. While some advocate the conservation of predators such as wolves and tigers, others see them as vermin and want them gone.
In this book, Hans Kruuk, a life-long naturalist with a passion for predators tells the fascinating story of carnivores and our intricate relationships with them. Illustrated with specially commissioned drawings, it deals with the wild beauty of carnivores and their conservation, but also with furs and medicine, man-eaters and sheep-killers, explaining in simple terms what the role of carnivores is in nature, how this impacts on human lives, our art and literature, how we instinctively respond to them and why.
Toon meer Toon minder. Recensie s 'Hunter and Hunted is aimed at a general audience and written to entertain as well as to inform and educate, achieving both aims rather well British Wildlife [Hans Kruk] hits a literary home run with his latest book Of the 25 species analysed, all weighing more than 15 kilograms, 15 had lost more than half their range. Up to nine of these species once roamed South and South-East Asia, but today large areas have lost them all.
The smallest declines were in the tundra and northern forests, where the relative scarcity of humans gives bears and wolves space to hunt. Most of the big beasts are now skulking on the margins of their former ranges, making them more vulnerable to extinction, says Wolf. But there are exceptions.
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Striped, spotted and brown hyenas have conceded only 15, 24 and 27 per cent respectively, and the grey wolf 26 per cent. In between, with losses of between 30 and 90 per cent, are various species of bears and big cats such as leopards, pumas and jaguars. But again, there are exceptions. In the case of predator-human conflict over depredation, Treves and Naughton-Treves [ 13 ] suggested that carnivore killing by hunters may actually promote conflict.
The process is thought to operate via shifts in age composition to younger age animals, which might depredate more because of higher encounter rates with livestock.
This process is thought to occur via the increased mobility of juvenile age classes of carnivores caused by decline in adult male territory tenure [ 14 ]. Moreover, hunting, culling or other lethal control targeted at specific individuals e. To confront these hypotheses, we examined a long-term dataset on human hunting of cougars and conflict involving cougars in BC, Canada. Cougar-human conflict and cougar hunting are relatively widespread and common, the latter attracting both local BC hunters as well as foreign hunters for guided hunts. We used this system to test whether: 1 cougars killed by hunters would be larger than those that came into conflict with people young animal hypothesis ; and 2 human hunting mortality and conflict incidence would be related problem animal and human hunting hypotheses.
We used a year dataset — on recorded cougar mortality in BC, Canada provided by the BC Ministry of Environment, wherein all records had an associated date. We used cougar kill records resulting from conflict and legal hunting events. For analyses involving age of conflict and legally hunted cougars [ 1 above] we used only those records with associated spatial data, sex and skull sizes.
The other analyses [ 2 above] were carried out using the larger dataset of spatially-referenced conflict and legal hunting mortalities of cougars with known sex, irrespective of whether skull size had been recorded.
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Only 96 illegal kills were recorded during —, of which 35 had associated skull length and width data and these were not used in analyses. We consider this a minimum estimate because evaluations of the frequency of illegal cougar kills have not been performed.
We do not expect illegal killing to vary across regions. Additional spatially-referenced mortality records of cougars with known sex , of which had associated skull information had unclear or unrecorded cause of death and were not used in analyses. After plotting kill locations by region in ArcGIS v. The larger dataset for analysis of cougar conflict in relation to human hunting levels included records. Skull size data length and width in mm were collected by BC Ministry of Environment personnel as a proxy for age.
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These variables are positively correlated [ 18 ] with the skull growth continuing long into adulthood [ 19 ]. To assess if skull sizes varied in relation to different human-caused mortality types, we first assessed if the variable was normally distributed with Shapiro—Wilk tests. Separate assessments were carried out for each sex and region. For males and females in all regions, the skull size variable was not normally distributed.
Therefore we used two-sample Wilcoxon rank-sum Mann—Whitney tests to compare mean skull size for conflict and hunter kills.
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We used time series analysis to test factor combinations hypothesized a priori to influence annual conflict frequency across time Additional file 1 : Table S1. Predictor variables included human density D , human hunting pressure annual number of cougars hunted in the year of conflict H t0 and the Normalized Difference Vegetation Index NDVI; a proxy for plant and prey productivity in the year of conflict N t0.
A squared term was included for human density D 2 to account for possible thresholds in human density beyond which conflict would decrease because of an assumed limitation to cougar habitat. Yearly lag 1 and 2 terms were used for human hunting pressure H t1 ; H t2 and NDVI N t1 ; N t2 to incorporate potential influences of hunting and habitat productivity in the periods preceding conflict. Human density calculation for the Vancouver Island region included a small part of the mainland coast as constrained by data availability.
Because habitat quality and prey availability can influence large carnivore-human conflict [ 24 , 25 ], but such data over our broad temporal and spatial extents were not available, we used NDVI as a habitat productivity surrogate [ 26 — 28 ]. We used the proportion of variance explained R 2 to evaluate model performance.
For all models that received support we plotted residuals against fitted values and inspected for patterns in the residual distribution. We used Stata v. Average skull sizes of cougars killed in five regions of British Columbia, Canada, as a result of conflict and human hunting.
Data include kill records with associated geographic coordinates and age skull size information for a males and b females. Note broken Y axis. Only for males in the Lower Mainland SW did the intercept-only model receive substantial support, but two candidate models were superior.
Hunter and Hunted: Relationships between Carnivores and People
Human hunting pressure in both current Figs. Human hunting was positively associated with conflict involving this cougar sex. Relative importance of variables associated with cougar-human conflict in British Columbia, Canada for a males and b females. Data are for a males and b females. Human hunting pressure was also the most important factor associated with cougar-human conflict for female cougars in 2 of 5 BC regions.
Only for one model female cougars, Thompson-Okanagan was increased human hunting lag 2 associated with decreased conflict. Estimates for which confidence intervals did not overlap zero have an asterisk. No reporting of coefficients refers to the specific variable s not being included in supported models. Human density was the key variable associated with conflict for female cougars in 3 BC regions Fig.
Years with intermediary human densities were generally associated with conflict Additional file 4 : Tables S9, S With expanding human populations and influence, conflict between carnivores and humans is expected to increase, which requires evidence-informed approaches to conflict mitigation.
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A long-term data set on human-caused cougar mortality allowed us to confront fundamental hypotheses on the relationship between human hunting, cougar-human conflict and cougar population demography, including testing of the commonly accepted but under-examined assumption that hunting of large carnivores could result in decreased conflict incidence see [ 34 ] for an overview and call for inquiry into the relationship between hunting of carnivores and conflict.
As we expected, we found support for the young animal hypothesis in most comparisons, with individuals that came into conflict with humans younger compared to those hunted. Human encroachment into cougar habitat increases conflict potential [ 35 — 37 ] and young animals are more likely to occur in areas used by people than other age classes [ 38 ].
Dispersing juveniles are more likely to come into conflict on travel routes through fragmented habitats and high risk areas including human inhabited areas, roads [ 39 ] and ranches [ 24 , 40 ]. In addition, food resources may be limited while dispersers attempt to establish home ranges [ 41 ].