Apparent demographic changes in black-tailed deer associated with wolf control on northern Vancouver Island

Hatter, Ian W.; Janz, Doug W.

doi:10.1139/z94-119

Cited by 41 publications

(37 citation statements)

References 11 publications

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“…Wolves and cougars on Vancouver Island prey mostly on black-tailed deer (Odocoileus hemionus hemionus (Rafinesque, 1817)) (Scott and Shackleton 1980;Gladders 2000), and deer abundance has fluctuated greatly over recent decades (Hatter and Janz 1994). Populations increased during the 1970s, perhaps due in part to newly available food resources in regenerating clearcuts (Bunnell 1990).…”

Section: Discussionmentioning

confidence: 99%

Timing and causes of mortality in the endangered Vancouver Island marmot (Marmota vancouverensis)

Bryant¹,

Page²

2005

Can. J. Zool.

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We used radiotelemetry to evaluate seasonal survival rates and mortality factors for a critically endangered island endemic, the Vancouver Island marmot (Marmota vancouverensis Swarth, 1911). Recovery of radio transmitters and marmot remains suggested that predation was the major cause of mortality, accounting for at least 24 of 29 (83%) known-fate deaths recorded since radiotelemetry efforts began in 1992. Wolves (Canis lupus L., 1758) and cougars (Puma concolor (L., 1771)) apparently accounted for 17 deaths (59%). Three marmots (10%) were killed by golden eagles (Aquila chrysaetos (L., 1758)), four (14%) were killed by unknown predators that probably included all of the above species, two (7%) died from unknown causes, and three (10%) died during hibernation in a single burrow. Mortality rates varied seasonally. The daily probability of death during hibernation was very low (P death = 0.016). The probability of death was also low from spring emergence through 31 July (P death = 0.051), but was eight times higher in August (P death = 0.395) and four times higher in September (P death = 0.175). We concluded that predation was the proximate cause of recent declines in wild Vancouver Island marmot populations, that losses were highly concentrated in late summer, and that previous studies exaggerated the importance of winter mortality. We suggest that high predation rates were associated with forestry and altered predator abundance and hunting patterns.Résumé : La radio-télémétrie nous a servi à évaluer le taux saisonnier de survie et les facteurs de mortalité chez la marmotte de l'île de Vancouver (Marmota vancouverensis Swarth, 1911), une espèce endémique insulaire fortement menacée. La récupération des émetteurs et des carcasses de marmottes laisse croire que la prédation est la cause principale de mortalité, représentant au moins 24 (83 %) des 29 cas étudiés depuis le début de l'utilisation de la radio-télé-métrie en 1992. Les loups (Canis lupus L., 1758) et les couguars (Puma concolor (L., 1771)) sont apparemment responsables de 17 (59 %) des morts. Trois (10 %) des marmottes ont été tuées par des aigles royaux (Aquila chrysaetos (L., 1758)) et quatre (14 %) par des prédateurs inconnus qui incluent peut-être toutes les espèces mentionnées pré-cédemment; deux (7 %) sont mortes de causes inconnues et trois (10 %) sont mortes dans un même terrier durant l'hibernation. Les taux de mortalité varient en fonction de la saison. La probabilité quotidienne de mortalité durant l'hibernation est très faible (P mort = 0,016). La probabilité de mortalité est aussi faible de l'émergence printanière jusqu'au 31 juillet (P mort = 0,051), mais elle est huit fois plus élevée en août (P mort = 0,395) et quatre fois plus élevée en septembre (P mort = 0,175). En conclusion, la prédation est la cause immédiate des déclins récents des populations sauvages de marmottes de l'île de Vancouver, les pertes sont fortement concentrées en fin d'été et les études antérieures ont exagéré l'importance de la mortalité hivernale. Nous croyons que ...

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Section: Discussionmentioning

confidence: 99%

Timing and causes of mortality in the endangered Vancouver Island marmot (Marmota vancouverensis)

Bryant¹,

Page²

2005

Can. J. Zool.

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“…Approximately 80% of these meadows have been lost due to habitat conversion after the 1850s (Lea 2006), prompting recent conservation and restoration efforts (Fuchs 2001, Devine et al 2007). Ungulate densities have increased in the region (MacDougall 2008) from 7-15 deer/km 2 (Cowan 1945) to 10-25 deer/km 2 more recently (Hatter and Janz 1994;T. These grasses produce live material and litter that inhibit native seed establishment and survival (MacDougall 2005, Mac-Dougall andTurkington 2005); whereas episodic biomass removals by cutting, weeding, or burning increase native species cover (MacDougall and Turkington 2007).…”

Section: Methodsmentioning

confidence: 99%

Herbivory More Limiting Than Competition on Early and Established Native Plants in an Invaded Meadow

Gonzales¹,

Arcese

2008

Ecology

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The dominance of nonnative plants coupled with declines of native plants suggests that competitive displacement drives extinctions, yet empirical examples are rare. Herbivores, however, can alter vegetation structure and reduce diversity when abundant. Herbivores may act on mature, reproductive life stages whereas some of the strongest competitive effects might occur at early life stages that are difficult to observe. For example, competition by perennial nonnative grasses can interfere with the establishment of native seeds. We contrasted the effects of ungulate herbivory and competition by neighboring plants on the performance of native plant species at early and established life stages in invaded oak meadows. We recorded growth, survival, and flowering in two native species transplanted as established plants, six native species grown from seed, and five extant lily species as part of two 2 x 2 factorial experiments that manipulated herbivory and competition. Herbivory reduced the performance of nearly all focal native species at early and established life stages, whereas competition had few measurable effects. Our results suggest that herbivory has a greater local influence on native plant species than competition and that reducing herbivore impacts will be required to successfully restore endangered oak meadows where ungulates are now abundant.

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“…Conversely, the quality of white-tailed deer habitat may have increased in response to human agricultural practices (Swenson et al 1983;Roseberry and Woolf 1998). Others have suggested stochastic events (e.g., severe winter, drought) (Unsworth et al 1999), hunting (McCorquodale 1999), and predation (Hatter and Janz 1994;Ballard et al 2001) as being capable of causing mule deer declines.…”

Section: Introductionmentioning

confidence: 99%

Cougar predation and population growth of sympatric mule deer and white-tailed deer

Robinson¹,

Wielgus²,

Gwilliam³

2002

Can. J. Zool.

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Mule deer (Odocoileus hemionus) populations throughout the west appear to be declining, whereas whitetailed deer (Odocoileus virginianus) populations are increasing. We compared abundance, number of fetuses per female (maternity rate), recruitment, and cause-specific adult (≥1 year old) mortality rate for sympatric mule deer and whitetailed deer in south-central British Columbia to assess population growth for each species. White-tailed deer were three times more abundant (908 ± 152) than mule deer (336 ± 122) (mean ± 1 SE). Fetal rates of white-tailed deer (1.83) were similar to those of mule deer (1.78). There was no statistically significant difference in recruitment of white-tailed deer (56 fawns : 100 does) and mule deer (38 fawns : 100 does). The annual survival rate for adult white-tailed deer (S WT = 0.81) was significantly higher than that for mule deer (S MD = 0.72). The main cause of mortality in both populations was cougar predation. The lower mule deer survival rate could be directly linked to a higher predation rate (0.17) than for white-tailed deer (0.09). The finite growth rate (λ) was 0.88 for mule deer and 1.02 for white-tailed deer. The disparate survival and predation rates are consistent with the apparent-competition hypothesis.Résumé : Les populations de cerfs mulets (Odocoileus hemionus) semblent être en déclin dans tout l'ouest, alors que celles des cerfs de Virginie (Odocoileus virginianus) augmentent. Nous avons comparé l'abondance, le taux de production de fétus, le taux de recrutement et les taux de mortalité des adultes ($1 an) attribuables à des causes spécifiques chez des cerfs mulets er des cerfs de Virginie vivant en sympatrie dans le centre sud de la Colombie-Britannique afin d'évaluer la croissance démographique de chacune de ces espèces. Les cerfs de Virginie sont trois fois plus abondants (908 ± 152) que les cerfs mulets (336 ± 122) (moyenne ± 1 erreur type). Le taux foetal est semblable chez les cerfs de Virginie (1,83) et les cerfs mulets (1,78). Il n'y a pas de différence statistiquement significative entre les taux de recrutement des cerfs de Virginie (56 faons : 100 femelles) et des cerfs-mulets (38 faons : 100 femelles). La survie annuelle des adultes est significativement plus élevée chez le cerf de Virginie (S WT = 0,81) que chez le cerf mulet (S MD = 0,72). La principale cause de mortalité chez les deux populations est la prédation exercée par les couguars. Le taux de survie plus faible du cerf mulet peut être relié directement à son taux de prédation plus élevé (0,17) que celui du cerf de Virginie (0,09). Le taux de croissance réel (8) est de 0,88 chez le cerf mulet et de 1,02 chez le cerf de Virginie. La disparité des taux de prédation et de survie est en accord avec l'hypothèse de la compétition apparente.[Traduit par la Rédaction] Robinson et al. 568

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Apparent demographic changes in black-tailed deer associated with wolf control on northern Vancouver Island

Cited by 41 publications

References 11 publications

Timing and causes of mortality in the endangered Vancouver Island marmot (Marmota vancouverensis)

Timing and causes of mortality in the endangered Vancouver Island marmot (Marmota vancouverensis)

Herbivory More Limiting Than Competition on Early and Established Native Plants in an Invaded Meadow

Cougar predation and population growth of sympatric mule deer and white-tailed deer

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