Prédation on red squirrels during a snowshoe hare decline

1995 ◽  
Vol 73 (4) ◽  
pp. 713-722 ◽  
Author(s):  
A. Kari Stuart-Smith ◽  
Stan Boutin
Keyword(s):  
Breeding Season ◽  
Population Decline ◽  
Population Cycles ◽  
Tamiasciurus Hudsonicus ◽  
Adult Survival ◽  
Snowshoe Hare ◽  
Juvenile Survival ◽  
Red Squirrel ◽  
Red Squirrels ◽  
Snowshoe Hares

We examined the extent and impact of predation on red squirrels (Tamiasciurus hudsonicus) during a cyclic decline of snowshoe hares in the southwestern Yukon, Canada. We monitored survival of squirrels on three control grids and a predator exclosure from March 1991 through August 1993. On controls, adult survival during the breeding season decreased from 1991, when snowshoe hare populations were high, to 1992, when hare populations declined rapidly. Survival increased slightly in 1993, when hare and predator populations were very low. Similarly, adult survival during winter was lower in 1992 – 1993 than in 1991 – 1992. Adult survival on the exclosure remained similar in each breeding season but declined during winter 1992 – 1993. Adult survival was similar on the controls and the exclosure in each year except during winter 1991–1992 and the 1992 breeding season, when it was lower on the controls. There was no difference in juvenile survival between the controls and the exclosure. Despite the decrease in adult survival due to predation, there was no population decline on any of the control grids. We conclude that predation did not have a measurable impact on red squirrel densities at Kluane and that it is unlikely red squirrels show 10-year population cycles in conjunction with snowshoe hares.

SEASONAL DAMAGE BY INSECTS AND SQUIRRELS TO FEMALE REPRODUCTIVE STRUCTURES OF BLACK SPRUCE, PICEA MARIANA (MILL.) B.S.P.

1988 ◽  
Vol 120 (12) ◽  
pp. 1113-1121 ◽  
Author(s):  
Y.H. Prévost ◽  
J.E. Laing ◽  
V.F. Haavisto
Keyword(s):  
Picea Mariana ◽  
Black Spruce ◽  
Choristoneura Fumiferana ◽  
Tamiasciurus Hudsonicus ◽  
Red Squirrel ◽  
Red Squirrels ◽  
Reproductive Structures ◽  
Cone Axis ◽  
Viable Seeds ◽  
Cone Growth

AbstractThe seasonal damage to female reproductive structures (buds, flowers, and cones) of black spruce, Picea mariana (Mill.) B.S.P., was assessed during 1983 and 1984. Nineteen insects (five Orders) and the red squirrel, Tamiasciurus hudsonicus (Erxleben), were found feeding on these reproductive structures. Collectively, these organisms damaged 88.9 and 53.5% of the cones in 1983 and 1984, respectively. In the 2 years, Lepidoptera damaged 61.8% of the cones in 1983 and 44.4% of the cones in 1984. The spruce budworm, Choristoneura fumiferana (Clem.), and the spruce coneworm, Dioryctria reniculelloides Mut. and Mun., were the most important pests. Cones damaged by Lepidoptera could be classed into three categories: (a) severe, yielding no seeds; (b) moderate, yielding 22.3 seeds per cone; and (c) light, yielding 37.5 seeds per cone. Undamaged cones yielded on average 39.9 seeds per cone. Red squirrels removed 18.8% of the cones in 1983 and none in 1984. The spruce cone axis midge, Dasineura rachiphaga Tripp, and the spruce cone maggot, Lasiomma anthracinum (Czerny), caused minor damage in both years. Feeding by spruce cone axis midge did not reduce cone growth significantly or the number of viable seeds per cone, but feeding by the spruce cone maggot did. During both years new damage by insects to the female reproductive structures of the experimental trees was not observed after mid-July. In 1983 damage by red squirrels occurred from early to late September. In 1984 damage to cones on trees treated with dimethoate was 15.6% compared with 53.5% for untreated trees, without an increase in the number of aborted cones.

Genetic structure of the arboreal squirrels (Glaucomys sabrinus and Tamiasciurus hudsonicus) in the North American Black Hills

2012 ◽  
Vol 90 (9) ◽  
pp. 1191-1200 ◽  
Author(s):  
A.M. Kiesow ◽  
E.M. Monroe ◽  
H.B. Britten
Keyword(s):  
Gene Flow ◽  
Genetic Structure ◽  
Management Practices ◽  
Allelic Diversity ◽  
Black Hills ◽  
Tamiasciurus Hudsonicus ◽  
Glaucomys Sabrinus ◽  
Red Squirrel ◽  
Isolated Populations ◽  
Red Squirrels

We selected two isolated mammalian populations, the Black Hills northern flying squirrel ( Glaucomys sabrinus (Shaw, 1801)) and red squirrel ( Tamiasciurus hudsonicus (Erxleben, 1777)), to elucidate their genetic structure. We trapped both squirrels from 2005 to 2007, in three regions of the Black Hills, differing in geology and vegetation, to collect ear samples for genetic analyses. Microsatellite loci (northern flying (9) and red squirrel (13)) were used to examine genetic structure. Data analyses estimated genetic variability, substructure, and gene flow. Northern flying and red squirrel populations have allelic diversity and observed heterozygosity similar to other isolated populations. Each species shows weak substructure from STRUCTURE and GENELAND analyses, suggesting squirrel movements may be inhibited by topography or unsuitable habitat. Recent gene flow estimates from BAYESASS indicate that both species experience some within population gene flow and red squirrels may be more structured than northern flying squirrels because of lower migration rates. Concordant patterns of genetic structure in northern flying and red squirrels indicate that other species’ movements in the Black Hills may be affected by topography and habitat. Because their habitat is isolated in the Black Hills, management practices and conservation measures are recommended to promote viability and survival of each species.

Body temperature dynamics of the red squirrel (Tamiasciurus hudsonicus): adaptations for energy conservation

1979 ◽  
Vol 57 (7) ◽  
pp. 1349-1354 ◽  
Author(s):  
Ronald W. Pauls
Keyword(s):  
Body Temperature ◽  
Motor Activity ◽  
Energy Conservation ◽  
Outdoor Environment ◽  
Tamiasciurus Hudsonicus ◽  
Rapid Decline ◽  
Red Squirrel ◽  
Red Squirrels ◽  
Air Temperatures ◽  
Temperature Dynamics

Abdominal temperatures (Tb) of two captive female red squirrels (Tamiasciurus hudsonicus) in a natural outdoor environment were monitored by radiotelemetry at air temperatures (Ta) from −33 to 28 °C. Abdominal temperature ranged from 35.9 to 41.4 °C with values usually less than 39 °C when an animal was in the nest and greater than 39 °C when outside. An increase of Tb to about 39 °C usually occurred before an animal left the nest. In the nest Tb was positively correlated with Ta. Outside the nest there was a weak positive correlation at Ta less than 15 °C and a stronger negative correlation at higher Ta. During subnivean activity a rapid decline in Tb usually occurred. It is suggested that in the nest a low Tb is adaptive in that it results in energy conservation while a higher Tb is required outside the nest for rapid and coordinated motor activity.

scholarly journals Cyclic dynamics of snowshoe hares on a small island in the Yukon

2002 ◽  
Vol 80 (8) ◽  
pp. 1442-1450 ◽  
Author(s):  
Charles J Krebs ◽  
Todd N Zimmerling ◽  
Claire Jardine ◽  
Kim A Trostel ◽  
Alice J Kenney ◽  
...  
Keyword(s):  
Population Decline ◽  
Survival Rates ◽  
Ground Squirrels ◽  
Adult Survival ◽  
Small Island ◽  
Juvenile Survival ◽  
Lower Amplitude ◽  
Arctic Ground Squirrels ◽  
Reproductive Rates ◽  
Survival Differences

Snowshoe hare (Lepus americanus) populations were monitored from 1977 to 2001 on Jacquot Island (5 km2) in Kluane Lake, southwestern Yukon, and on nearby mainland sites. Jacquot Island hares averaged twice the density of mainland control populations and, although they show 10-year cycles, fluctuate with much lower amplitude than mainland populations. Three separate intensive studies over 6 years attempted to determine what caused these differences. We tested two hypotheses to explain the dynamics. Reproductive rates of hares were similar on Jacquot Island and the mainland. Adult survival rates were higher on the island in most years, with the exception of years of population decline. Juvenile survival rates from 0 to 30 days of life were much higher on the island than on the mainland except for decline summers. The adult- and juvenile-survival differences between the island and the mainland were explained most consistently by predation. Improved survival on the island is correlated with a reduction in the numbers and types of predators found on Jacquot Island compared with the mainland. In particular, red squirrels were rare on Jacquot Island, arctic ground squirrels were absent, and the larger predators, like lynx and great-horned owls, were sporadic in occurrence on this small island.

Behavioural strategies relevant to the energy economy of the red squirrel (Tamiasciurus hudsonicus)

1978 ◽  
Vol 56 (7) ◽  
pp. 1519-1525 ◽  
Author(s):  
Ronald W. Pauls
Keyword(s):  
Locomotor Activity ◽  
Air Temperature ◽  
Activity Patterns ◽  
Tamiasciurus Hudsonicus ◽  
Temperature Cycle ◽  
Red Squirrel ◽  
Red Squirrels ◽  
Time Out ◽  
Energy Economy ◽  
Behavioural Strategies

Amount and intensity of locomotor activity and time out of the nest were measured for a 1-year period on captive red squirrels (Tamiasciurus hudsonicus) under natural conditions. Daily and annual activity patterns and correlations between activity and meteorological variables were examined. A pronounced annual cycle, in phase with the annual temperature cycle, was found in all three aspects of activity. Daily amount of locomotor activity and time out of the nest were closely correlated with mean daily air temperature. Wind, photoperiod, and air temperature during the preceding week showed a weak but significant correlation with activity. Daily patterns of activity varied seasonally from a distinctly bimodal to a unimodal pattern, with a shift in winter to more midday activity. The relevance of these behavioural strategies to the energy economy of the red squirrel is discussed.

POPULATION STRUCTURE AND BODY WEIGHTS OF SNOWSHOE HARES ON MANITOULIN ISLAND, ONTARIO

1964 ◽  
Vol 42 (6) ◽  
pp. 975-986 ◽  
Author(s):  
Robin Newson ◽  
Antoon de Vos
Keyword(s):  
Body Weight ◽  
Population Structure ◽  
Breeding Season ◽  
Age Structure ◽  
Annual Cycle ◽  
Snowshoe Hare ◽  
Adult Females ◽  
Snowshoe Hares ◽  
Body Weights ◽  
Previous Summer

The age structure and body weight of two snowshoe hare populations, just at or passing a cyclical peak in numbers, were studied over 3 years. The survival of the young was poor. Each winter, the young of the previous summer were already too few to replace all the normally expected losses of adults. Numbers therefore decreased from year to year. Shot samples were biased towards adult females in the breeding season. It appeared that they were feeding more heavily than the males as their gut weights at this time were markedly increased. There was a clear annual cycle in body weight with females consistently heavier than males. Immature hares were lighter than adults during their first winter and remained so until they were at least a year old.

Female Red Squirrel (Tamiasciurus hudsonicus) Reproductive Tracts from Fenitrothion Treated and Untreated Forest of Southeastern New Brunswick

1986 ◽  
Vol 62 (4) ◽  
pp. 233-235 ◽  
Author(s):  
Louis LaPierre
Keyword(s):  
New Brunswick ◽  
Coniferous Forest ◽  
Tamiasciurus Hudsonicus ◽  
Corpora Lutea ◽  
Red Squirrel ◽  
Probability Level ◽  
Red Squirrels ◽  
August 15Th ◽  
Student’S T ◽  
Student’S T Test

Between August 15th and September 15th 1979, 1980 and 1981, 77 and 74 red squirrels, Tamiasciurus hudsonicus, were captured within the sprayed and unsprayed coniferous forest of southeastern New Brunswick. Following live capture, the squirrels were sacrificed, weighed and the reproductive tracts were removed and preserved in a 10% formalin solution.Counts of placental scars and corpora lutea of squirrels that inhabited the sprayed forest had a mean placental scar count of 3.8 and a mean corpora lutea count of 4.2. Squirrels from the unsprayed coniferous forest had a mean placental count of 3.6 and a corpora lutea count of 3.9. Statistical analyses, using the student's T-test with a probability level of 0.05, revealed no significant differences in reproductive success of the two groups of squirrels.

Effect of temperature and acclimation upon FFA levels in three species of rodents

1971 ◽  
Vol 49 (3) ◽  
pp. 303-305 ◽  
Author(s):  
J. Homer Ferguson ◽  
G. Edgar Folk Jr.
Keyword(s):  
Cold Acclimation ◽  
Cold Exposure ◽  
Tamiasciurus Hudsonicus ◽  
Effect Of Temperature ◽  
Red Squirrel ◽  
Short Term ◽  
Red Squirrels ◽  
White Rats ◽  
Short Term Exposure ◽  
Rats And Mice

Free fatty acid (FFA) levels were determined in warm- and cold-acclimated white rats, mice, and red squirrels (Tamiasciurus hudsonicus). FFA concentrations of the genetically cold-adapted species (red squirrel) were highest and reflect its ability to maintain high metabolic rates reported by others. In the red squirrels, FFA concentrations were elevated after cold acclimation. Acclimation of white rats and mice had no effect on FFA levels. Short-term cold exposure (−35 °C) caused the FFA levels to rise in all three species. Cold-exposed mice were found to be highest in plasma FFA content. The ability of the red squirrels to mobilize FFA during short-term exposure was enhanced by cold acclimation. The response of rats and mice to cold exposure was not changed by acclimation. This would indicate a greater capacity of the red squirrel to respond to acclimating conditions.

scholarly journals Population fragmentation leads to morpho-functional variation in British red squirrels (Sciurus vulgaris)

2019 ◽  
Author(s):  
Philip G. Cox ◽  
Philip J.R. Morris ◽  
Andrew C. Kitchener
Keyword(s):  
Functional Divergence ◽  
Population Decline ◽  
Red Squirrel ◽  
Population Fragmentation ◽  
Sciurus Vulgaris ◽  
Functional Variation ◽  
Linear Measurements ◽  
Red Squirrels ◽  
Geometric Morphometric ◽  
The Uk

AbstractIt is well-known that population fragmentation and isolation can lead to rapid morphological and functional divergence, with the effect being particularly well-documented in rodents. Here, we investigated whether such a phenomenon could be identified in the Eurasian red squirrel (Sciurus vulgaris), which was once widespread across the majority of Great Britain, but suffered a severe population decline across the 20th century, leaving a highly fragmented distribution. The aim was to test for morphological and biomechanical variation of the mandible between the remaining British red squirrel populations. Linear and geometric morphometric methods were used to analyse shape in a sample of over 250 squirrel mandibles from across the UK and Germany. Canonical variates analysis identified significant shape differences between most British red squirrel populations, but particularly between squirrels from Formby and those from other populations. Linear measurements showed that Formby red squirrels have a significantly lower mechanical advantage of the temporalis muscle, indicating that they are less efficient at gnawing. We suggest that this difference may be related to past supplemental feeding of Formby squirrels with peanuts, which are less mechanically resistant than food items that occur naturally in the diet of British red squirrels.

scholarly journals Why do North American Red Squirrel, Tamiasciurus hudsonicus, Mothers Relocate Their Young? A Predation-based Hypothesis

2008 ◽  
Vol 122 (1) ◽  
pp. 65 ◽  
Author(s):  
Tricia Kerr ◽  
Sébastien Descamps
Keyword(s):  
North American ◽  
Tamiasciurus Hudsonicus ◽  
Red Squirrel ◽  
Red Squirrels ◽  
Efficient Strategy ◽  
North American Red Squirrels ◽  
The Impact ◽  
North American Red Squirrel

Our study reports the first observations consistent with Short-Tailed Weasel predation on juvenile North American Red Squirrels in the nest. Red Squirrel mothers are known to relocate their young to another nest after a disturbance. We suggest that this behaviour might be an efficient strategy that reduces the impact of litter depredation by weasels.

Sign in / Sign up

Export Citation Format

Share Document