USGS · 5221371
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Charles J. Henny, J. R. Bean, R.W. Fyfe. 1976. Elevated heptachlor epoxide and DDE residues in a merlin that died after migrating. https://pubs.usgs.gov/publication/5221371
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During the past few decades, Gray Wolves ( Canis lupus ) have recolonized many areas in the United States and Europe. In many other cases, however, although dispersing wolves reached areas with adequate prey, a population failed to recolonize. Herein, we provide a case study detailing how a wolf pack attempted for three years to recolonize an area 55 km from a long-established population and within 25 km of Minneapolis and St. Paul, Minnesota, but failed. The pack produced three litters of pups and at one time included 11–19 members, but it preyed on livestock and dogs and, consequently, was lethally removed. The history of this pack’s attempt to recolonize an area long devoid of wolves exemplifies the issues that have prevented earlier recolonizations in non-wild lands in Minnesota and elsewhere and that promise to do so well into the future.
A free-ranging Gray Wolf (Canis lupus), habituated to human presence (the author) on Ellesmere Island, Canada, learned to anticipate experimental feeding by a human, became impatient, persistent, and bold and exhibited stalking behaviour toward the food source. Only after the author offered the wolf about 90 clumps of dry soil over a period of 45 minutes in three bouts, did the wolf give up this behaviour. To my knowledge, this is the first example of extinguishing a learned response in a free-ranging wolf and provides new insight into the learning behaviour of such animals.
Moose ( Alces americanus ) in northeastern Minnesota have declined by 55% since 2006. Although the cause is unresolved, some studies have suggested that Gray Wolves ( Canis lupus ) contributed to the decline. After the Moose decline, wolves could either decline or switch prey. To determine which occurred in our study area, we compared winter wolf counts and summer diet before and after the Moose decline. While wolf numbers in our study area nearly doubled from 23 in winter 2002 to an average of 41 during winters 2011–2013, calf:cow ratios (the number of calves per cow observed during winter surveys) in the wider Moose range more than halved from 0.93 in 2002 to an average of 0.31 during 2011–2013. Compared to summer 2002, wolves in summers 2011–2013 consumed fewer Moose and more White-tailed Deer ( Odocoileus virginianus ). While deer densities were similar during each period, average vulnerability, as reflected by winter severity, was greater during 2011–2013 than 2002, probably explaining the wolf increase. During the wolf increase Moose calves remained a summer food item. These findings suggest that in part of the Moose range, deer subsidized wolf numbers while wolves also preyed on Moose calves. This contributed to a Moose decline and is a possible case of apparent competition and inverse-density-dependent predation.