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

2005 ◽  
Vol 83 (5) ◽  
pp. 674-682 ◽  
Author(s):  
Andrew A Bryant ◽  
Rick E Page
Keyword(s):  
Puma Concolor ◽  
Survival Rates ◽  
Late Summer ◽  
Vancouver Island ◽  
Winter Mortality ◽  
Mortality Factors ◽  
Proximate Cause ◽  
Island Endemic ◽  
Radio Transmitters ◽  
Probability Of Death

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 (Pdeath = 0.016). The probability of death was also low from spring emergence through 31 July (Pdeath = 0.051), but was eight times higher in August (Pdeath = 0.395) and four times higher in September (Pdeath = 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.

Winter mortality and the function of larval hibernacula during the 14-year life cycle of an arctic moth, Gynaephora groenlandica

1995 ◽  
Vol 73 (4) ◽  
pp. 657-662 ◽  
Author(s):  
Olga Kukal
Keyword(s):  
Plant Cover ◽  
Late Summer ◽  
High Arctic ◽  
The Arctic ◽  
Mortality Factor ◽  
Winter Mortality ◽  
Mortality Factors ◽  
Primary Host ◽  
Larval Behaviour ◽  
Gynaephora Groenlandica

Larvae of the arctic moth Gynaephora groenlandica stop feeding and spin silk hibernacula before the peak of summer season in the Canadian High Arctic Archipelago. This study examines the function of these hibernacula in relation to the biotic and abiotic mortality factors of parasitism and temperature. Winter mortality of 10% among larvae in cages on the tundra was compared with previous results on parasitism (56% mortality). Prior to winter, the cages were used to record larval behaviour and the location of hibernacula. The majority of the larvae (81%) spun hibernacula, most of which were concealed between the stems of arctic heather, Cassiope tetragona. Fewer hibernacula were found on the primary host plant, arctic willow, Salix arctica, than on C. tetragona or Dryas integrifolia, which formed the dominant plant cover. Nearly one-half of all the larvae that spun hibernacula made joint hibernacula with other larvae. Frequency of larvae sharing hibernacula declined with increasing numbers of larvae per cage. At low population density about half of the larvae occupied communal hibernacula, whereas only one-quarter of the larvae at high density shared hibernacula. In most cases only 2 larvae spun a common hibernaculum, 3 larvae shared hibernacula less frequently, and greater numbers of larvae were rarely found in a single hibernaculum. Unlike the high excess body temperatures usually achieved through thermoregulation by feeding larvae and pupae, temperatures within hibernacula were nearly identical with those of the surrounding substrate over 18 h and rose < 5 °C during the afternoon. This study suggests that larval hibernacula lower summer and winter mortality of G. groenlandica larvae. Hibernacula are an effective barrier to parasitism, which is the primary mortality factor. Furthermore, the behavioural shift from feeding to spinning hibernacula may prevent energy depletion by inducing metabolic depression during mid to late summer, which may be essential for winter survival.

scholarly journals Morphology and Population Characteristics of Vancouver Island Cougars, Puma concolor vancouverensis

2004 ◽  
Vol 118 (2) ◽  
pp. 159
Author(s):  
Steven F. Wilson ◽  
Apryl Hahn ◽  
Aaron Gladders ◽  
Karen M. L. Goh ◽  
David M. Shackleton
Keyword(s):  
Body Size ◽  
Pacific Northwest ◽  
Puma Concolor ◽  
Survival Rates ◽  
Vancouver Island ◽  
Population Characteristics ◽  
Top Predator ◽  
Adult Females ◽  
The Pacific ◽  
Age And Sex

Cougars are a management concern on Vancouver Island because they are a top predator and because there have been frequent attacks on humans on the island. However, little is known about Cougar ecology in the Pacific Northwest of North America. We studied Cougar morphology and population characteristics as part of a larger study in two areas on Vancouver Island. We derived a multivariate measure of body size to describe changes with age and sex. Body size was similar in the two study areas. Survival rates for adult females were higher than those reported elsewhere; however, hunters avoided shooting females in general, and radio-collared Cougars in particular. Litter size at first detection was lower than reported in many other studies and may be related to food availability.Includes erratum for a figure in this article.

Life History and Habits of a Midge, Phytophaga thujae Hedlin (Diptera: Cecidomyiidae) in Western Red Cedar Cones

1964 ◽  
Vol 96 (7) ◽  
pp. 950-957 ◽  
Author(s):  
A. F. Hedlin
Keyword(s):  
British Columbia ◽  
Life History ◽  
Larval Stage ◽  
Late Summer ◽  
Vancouver Island ◽  
Thuja Plicata ◽  
Mortality Factors ◽  
Pupal Development ◽  
Red Cedar ◽  
Western Red Cedar

AbstractThe midge, Phytophaga thujae Hedlin, is a common pest in cones of western red cedar, Thuja plicata Donn. In some years nearly 100% of cones in localities on Vancouver Island, British Columbia, are infested.Adults emerge in March and April to oviposit on young cones. Eggs hatch during April and May. Larvae feed on seeds and scales, and in late summer spin cocoons in the cones, in which to overwinter. Prepupal and pupal development occur during winter.Mortality factors include parasites and competition. Species of Torymus and Tetrastichus parasitize larvae of the midge. In years of severe infestation, competition in early stages can cause considerable mortality.A portion of the population may remain in diapause in the larval stage each year.

scholarly journals Long-Term Study of Apparent Survival in Pacific Golden-Plovers at a Wintering Ground on Oahu, Hawaiian Islands

The Auk ◽  
2001 ◽  
Vol 118 (2) ◽  
pp. 342-351 ◽  
Author(s):  
Oscar W. Johnson ◽  
Phillip L. Bruner ◽  
Jay J. Rotella ◽  
Patricia M. Johnson ◽  
Andrea E. Bruner
Keyword(s):  
Survival Rates ◽  
Winter Mortality ◽  
Apparent Survival ◽  
Open Population ◽  
Long Term Study ◽  
Minimum Age ◽  
Parsimonious Model ◽  
Territorial Status ◽  
Breeding Seasons ◽  
Wintering Ground

Abstract We monitored the apparent survival of territorial and nonterritorial Pacific Golden-Plovers (Pluvialis fulva) for 20 consecutive nonbreeding seasons at a wintering ground within Bellows Air Force Station (BAFS) on the eastern shore of Oahu, Hawaii. Territorial birds were especially site-faithful from season to season, and each surviving individual reoccupied the same territory held in previous seasons. On average, territorial birds were resighted for about twice as many postbanding seasons (4.2) as nonterritorial birds (1.8). Open-population modeling indicated that apparent survival varied by age and territorial status. Our most parsimonious model estimated apparent annual survival rates in territorial plovers as 0.90 for young birds (age determined from retained juvenal primaries) from their first through their second wintering season, and 0.80 for adults over numerous seasons. For nonterritorial plovers, the corresponding values were 0.82 and 0.67, respectively. Despite lower apparent survival in nonterritorial plovers, it remains uncertain whether nonterritoriality actually results in shorter life spans. Some surviving nonterritorial birds may have gone undetected (detection probability of 0.70) because of permanent emigration from the study area. Given strong site-fidelity of territorial birds and the relative certainty of detecting them (probability = 1.0), we regarded the disappearance of a plover from its territory as an indicator of mortality. From last-recorded sightings, we concluded that territorial birds died with about equal frequency during the nonbreeding and breeding seasons. Because the latter is of much shorter duration, time-relative hazards were greatest while birds were away from the wintering grounds. Winter mortality was caused by accidents (collisions with overhead wires and other obstructions), and probable predation by owls. We estimated mean additional life expectancy among territorial plovers at 5.1 years for first-year birds, and 4.5 years for unknown-age adults. The oldest known-age individual was a male that lived 13 years 10 months; in adults of uncertain ages, one male survived to a minimum age of 18 years 10 months, and two females to at least 17 years 10 months. Pacific Golden-Plovers wintering at BAFS, especially territorial birds, demonstrated relatively high rates of apparent survival combined with adaptability for coexistence with humans in an urban environment.

scholarly journals Ready for bed: pre-hibernation movements and habitat use by Fowler’s Toads (Anaxyrus fowleri)

2018 ◽  
Vol 132 (1) ◽  
pp. 46-52
Author(s):  
David M. Green ◽  
Katharine T. Yagi
Keyword(s):  
Habitat Use ◽  
Global Positioning System ◽  
Late Summer ◽  
The Body ◽  
Positioning System ◽  
Radio Tracking ◽  
Water Line ◽  
Global Positioning ◽  
Radio Transmitters ◽  
Early Fall

We used radio-tracking to investigate movement patterns and habitat use of Fowler’s Toads (Anaxyrus fowleri) during late summer and early fall in a relatively undisturbed lakeshore dune and beach habitat at Long Point, Ontario. Small radio transmitters were fitted to 11 adult toads with an external harness made from fine surgical plastic tubing wrapped around the body behind the front limbs. We located radio-tagged toads morning and evening, for a maximum of 9 days, recording their locations using Global Positioning System units. Initially, the toads were located on the upper beach or in the fore-dunes during the day, either dug in under the sand or hiding beneath debris; in the evening, they were generally active on the lower beach close to the water line. After a storm and the onset of cooler autumn weather, the toads tended to move further from the water line. They also curtailed their nightly activity and retreated deeper into the sand. As this sort of behaviour was not observed during the summer, we interpret it as pre-hibernation movement to more stable sites away from the beach where the animals can burrow deeply into the sand to lie dormant during the winter.

Impact of helminth parasitism on a snowshoe hare population in central Wisconsin: a field experiment

1995 ◽  
Vol 73 (10) ◽  
pp. 1891-1898 ◽  
Author(s):  
Sara E. M. Bloomer ◽  
Thomas Willebrand ◽  
Ingegerd M. Keith ◽  
Lloyd B. Keith
Keyword(s):  
Survival Rates ◽  
Snowshoe Hare ◽  
Marrow Fat ◽  
Proximate Cause ◽  
Risk Of Death ◽  
Snowshoe Hares ◽  
Condition Indices ◽  
Time Specific ◽  
And Control ◽  
Hare Population

We tested the hypothesis that helminth parasitism is demographically significant to a noncyclic population of snowshoe hares (Lepus americanus) near the species' geographic boundary in central Wisconsin (U.S.A.). During November 1988 to December 1991, we injected 93 individuals (≥760 g, aged ≥2 months) with anthelmintics: Ivermectin for nematode and Droncit for cestode infections. We injected 98 control hares with propylene glycol, the common vehicle for both drugs. All treated and control hares were radio-collared with mortality-sensing transmitters and monitored daily to weekly from the ground or air. Prevalence and intensity of lungworms (Protostrongylus boughtoni), intestinal worms (Nematodirus triangularis), and stomach worms (Obeliscoides cuniculi) were markedly reduced by Ivermectin treatment. No other nematodes were found to be present. Treatment with Droncit to remove intestinal cestodes was apparently unnecessary, as prevalence among necropsied untreated hares and controls was just 10%. We compared body-condition indices (mass changes, response to trap stress, and bone-marrow fat), reproduction (pregnancy rate and litter size), home-range sizes, and time-specific survival rates of anthelmintic-treated versus control hares. None of these demographic variables differed significantly between treated and control cohorts, nor was there any evidence that parasitism increased the risk of death from predation, which was the proximate cause of 96% of all natural mortalities. We conclude that helminth parasitism played no detectable role in the dynamics of this Wisconsin snowshoe hare population.

Impact of puma predation on the decline and recovery of a mule deer population in southeastern Idaho

2006 ◽  
Vol 84 (11) ◽  
pp. 1555-1565 ◽  
Author(s):  
J.W. Laundré ◽  
L. Hernández ◽  
S.G. Clark
Keyword(s):  
Population Change ◽  
Puma Concolor ◽  
Mule Deer ◽  
Odocoileus Hemionus ◽  
Winter Mortality ◽  
Deer Population ◽  
Before And After ◽  
Proximate Factor ◽  
A Minor ◽  
The Impact

We modeled the impact of puma ( Puma concolor (L., 1771)) predation on the decline and recovery of mule deer ( Odocoileus hemionus (Rafinesque, 1817)) in southern Idaho based on estimates of puma numbers, predation rates of pumas, and reproductive variables of deer. Deer populations peaked in 1992–1993, then declined more than 55% and remained low for the next 11 years. Puma numbers peaked 4–6 years after deer populations peaked but then declined to original levels. Estimated puma predation on the deer population before and after the decline was 2.2%–3.3% and 3.1%–5.8%, respectively. At high puma densities (>3 pumas/100 km2), predation by pumas delayed deer recovery by 2–3 years. Percent winter mortality of fawns (r2 = 0.62, P < 0.001) and adult female deer (r2 = 0.68, P < 0.001) correlated positively with December–January snowfall. Incorporation of winter snowfall amounts in the model produced a pattern of deer population change matching estimated changes based on field survey data. We conclude that pumas probably were a minor factor in the decline of the deer population in our area and did not suppress deer recovery. We propose that winter snowfall was the primary ultimate and proximate factor in the deer decline and suppression of their recovery.

Survival of juvenile hares during a cyclic population increase

1998 ◽  
Vol 76 (10) ◽  
pp. 1949-1956 ◽  
Author(s):  
Elizabeth A Gillis
Keyword(s):  
Cause Of Death ◽  
Food Availability ◽  
Survival Rates ◽  
Lepus Americanus ◽  
Population Increase ◽  
Differential Survival ◽  
Proximate Cause ◽  
Supplemental Food ◽  
Snowshoe Hares ◽  
And Control

Snowshoe hares (Lepus americanus) are multilittered synchronous breeders that produce up to four distinct litters of young each summer. I used radiotelemetry to determine the effects of juvenile cohort (i.e., litter group) and food availability on postweaning survival of hares in the southwestern Yukon during the increase phase of a hare cycle. During the study, I monitored 86 juvenile hares from control areas and areas in which supplemental food was provided. Twenty-eight-day survival did not differ between food addition and control areas for any juvenile cohort, and survival rates of juveniles (all cohorts combined) did not differ significantly from those of adults (juveniles: 0.91 per 28 days; adults: 0.93 per 28 days). However, when examined by juvenile cohort, survival of third and fourth litters was significantly lower than that of adults and first and second litters. These differences were the result of differential survival among the juvenile cohorts during a 3-month period in the fall (September-November). Predation was the primary proximate cause of death for weaned juvenile hares, accounting for 86% of deaths.

Survival and growth of four amabilis fir stock types on Vancouver Island

1991 ◽  
Vol 67 (2) ◽  
pp. 147-154 ◽  
Author(s):  
F. T. Pendl ◽  
B. N. D'Anjou
Keyword(s):  
Root Growth ◽  
Lateral Roots ◽  
Survival Rates ◽  
Field Performance ◽  
Vancouver Island ◽  
Growth Capacity ◽  
Root Growth Capacity ◽  
Stock Type ◽  
Stock Types ◽  
Initial Root

Four stock types of amabilis fir (Abies amabilis) planted on Vancouver Island were compared for root growth capacity and field performance. Initial root growth capacity ratings and field performance of the stock types after five years differed significantly. Ranking the stock types by decreasing survival, stem height and diameter: 1 + 1 PBR 211 (89.4%, 78 cm, 15.7 mm), 1 + 0 PSB 313 (79.7%, 73 cm, 13.8 mm), 1 + 0 PSB 211 (76.8%, 66 cm, 12.9 mm) and 2 + 0 BR (58.9%, 59 cm, 11.0 mm). Given current nursery and planting costs and survival rates, the 1 + 0 PSB 313 and 211 are least expensive reforestation options, the 2 + 0 BR and 1 + 1 PBR 211 the most expensive. Root form of samples of each stock type lack well developed tap and lateral roots with root spiralling evident in the styroblock stock. Key words: Amabilis fir, stock types, bareroot, styroblock plugs

scholarly journals Spatial and temporal covariability in early ocean survival of Chinook salmon (Oncorhynchus tshawytscha) along the west coast of North America

2014 ◽  
Vol 71 (7) ◽  
pp. 1671-1682 ◽  
Author(s):  
D. Patrick Kilduff ◽  
Louis W. Botsford ◽  
Steven L. H. Teo
Keyword(s):  
Chinook Salmon ◽  
Oncorhynchus Tshawytscha ◽  
Survival Rates ◽  
Central Valley ◽  
Vancouver Island ◽  
Regional Patterns ◽  
Migration Patterns ◽  
The Pacific ◽  
Spatial Coverage ◽  
Correlation Scale

Abstract Knowledge of the spatial and temporal extent of covariation in survival during the critical ocean entry stage will improve our understanding of how changing ocean conditions influence salmon productivity and management. We used data from the Pacific coastwide coded-wire tagging program to investigate local and regional patterns of ocean survival of Chinook salmon (Oncorhynchus tshawytscha) from the Central Valley of California to southeastern Alaska from 1980–2006. Ocean survival of fish migrating as subyearlings covaried strongly from Vancouver Island to California. Short-term correlations between adjacent regions indicated this covariability increased, beginning in the early 1990s. Chinook salmon survivals exhibited a larger spatial scale of variability (50% correlation scale: 706 km) than those reported for other northeast Pacific Ocean salmon. This scale is similar to that of environmental variables related to ecosystem productivity, such as summer upwelling (50% correlation scale: 746 km) and sea surface temperature (50% correlation scale: 500–600 km). Chinook salmon ocean survival rates from southeastern Alaska and south of Vancouver Island were not inversely correlated, in contrast to earlier observations based on catch data, but note that our data differ in temporal and spatial coverage from those studies. The increased covariability in Chinook salmon ocean survival suggests that the marine phase contributes little to the reduction in risk across populations attributable to the portfolio effect. In addition, survival of fish migrating as yearlings from the Columbia River covaried with Chinook salmon survival from the northernmost regions, consistent with our understanding of their migration patterns.

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