Differential predation by coyotes on snowshoe hares

2001 ◽  
Vol 79 (10) ◽  
pp. 1878-1884 ◽  
Author(s):  
Karen E Hodges
Keyword(s):  
Body Mass ◽  
Natural Experiment ◽  
Canis Latrans ◽  
Lepus Americanus ◽  
Previous Experience ◽  
Age Classes ◽  
Snowshoe Hares ◽  
Differential Predation ◽  
Per Se ◽  
Prey Naiveté

Differential predation on particular sex or age classes of a population can arise as a result of predator preferences or prey attributes. I examined the impacts of age, size, and body mass of snowshoe hares, Lepus americanus, on their susceptibility to predation by coyotes, Canis latrans. I observed coyote predation on naïve radio-collared hares during a fortuitous natural experiment: a coyote entered a predator exclosure fence in which hares of all ages had no previous experience with terrestrial predators, thus separating age from experience with this predator. I contrasted this manipulation with populations in which hares grew up in the presence of coyotes. Prey naiveté per se did not influence coyote predation, but older hares appeared to be more susceptible to coyote predation than younger ones. There were no obvious effects of body mass or size on coyote predation during the winter.

Dynamics of a snow shoe hare population in fragmented habitat

1993 ◽  
Vol 71 (7) ◽  
pp. 1385-1392 ◽  
Author(s):  
Lloyd B. Keith ◽  
Sara E. M. Bloomer ◽  
Tomas Willebrand
Keyword(s):  
Patch Size ◽  
Canis Latrans ◽  
Lepus Americanus ◽  
Fragmented Habitat ◽  
Proximate Cause ◽  
Lower Survival ◽  
The Third ◽  
Snowshoe Hares ◽  
Poorly Drained Soils ◽  
Hare Population

During November 1988 – December 1991 we livetrapped, radio-collared, and monitored the survival, reproduction, and movements of snowshoe hares (Lepus americanus) in highly fragmented habitat near the species' geographic limit in central Wisconsin. Our 7 study areas centered on 5- to 28-ha patches of prime habitat: dense stands of willow (Salix), alder (Alnus), and regenerating aspen (Populus) on poorly drained soils. Maximum hare densities averaged 1.6 – 0.8/ha, and were unrelated to patch size. Rapid declines to extinction occurred on 3 of the 5 smallest study areas; on another, where extinction seemed imminent, juvenile ingress restored the population. On the 2 largest areas (23 – 28 ha of prime habitat) hare populations were stationary during the first 2 years, but declined by 50 – 70% in the third as mean annual (September – August) survival of radio-collared hares fell from 0.27 (1988 – 1990) to 0.07 (1990 – 1991). Annual survival on the 3 extinction sites averaged just 0.015 compared with 0.179 elsewhere. Reproduction did not differ between small (5 – 7 ha) vs. larger (23 – 28 ha) patches nor between years. Estimated dispersal of adult and juvenile hares from the 5 small study areas was twice as high as from the 2 larger, viz. 16 vs. 35% annually. Dispersers appeared to have markedly lower survival. Predation, chiefly by coyotes (Canis latrans), was the proximate cause of 96% (117 of 122) of natural deaths among radio-collared hares, and was therefore the overwhelming determinant of survival and thus population trend. Results of this study suggest that probabilities of extinction in such fragmented habitat depend importantly on patch size and attendant hare numbers; i.e., fall populations of < 10 hares frequenting patches of prime habitat ≤ 5 ha are not likely to persist long without ingress.

Prey selection and habitat partitioning in sympatric coyote and red fox populations, southwest Yukon

1989 ◽  
Vol 67 (5) ◽  
pp. 1285-1290 ◽  
Author(s):  
John B. Theberge ◽  
Chris H. R. Wedeles
Keyword(s):  
Vulpes Vulpes ◽  
Red Fox ◽  
Canis Latrans ◽  
Prey Selection ◽  
Lepus Americanus ◽  
Habitat Partitioning ◽  
Alternative Prey ◽  
Red Foxes ◽  
Snowshoe Hares ◽  
Selection Of

Sympatric coyotes (Canis latrans) and red foxes (Vulpes vulpes) in the southwest Yukon, studied across the peak of a snow-shoe hare (Lepus americanus) cycle, differed little from one another in prey selection, and both were heavily dependent on snowshoe hares. After the hare crash, however, foxes turned more to alternative prey than did coyotes. Foxes and coyotes differed in their selection of habitat patches and use of edge. Coyotes exploited edges, where hares were most abundant, and open communities, whereas foxes showed no significant use of edge and used brushy communities. The coexistence of red foxes and coyotes in the southwest Yukon may be facilitated by balancing competitive abilities: foxes persist because of elasticity in their choice of prey and coyotes persist by dominating edges.

scholarly journals Morphological determinants of jumping performance in the Iberian green frog

2019 ◽  
Vol 66 (4) ◽  
pp. 417-424
Author(s):  
Gregorio Moreno-Rueda ◽  
Abelardo Requena-Blanco ◽  
Francisco J Zamora-Camacho ◽  
Mar Comas ◽  
Guillem Pascual
Keyword(s):  
Body Size ◽  
Body Mass ◽  
Fluctuating Asymmetry ◽  
Hind Limb ◽  
Limb Length ◽  
Age Classes ◽  
Jumping Performance ◽  
Hind Limbs ◽  
Selective Forces ◽  
Pelophylax Perezi

Abstract Predation is one of the main selective forces in nature, frequently selecting potential prey for developing escape strategies. Escape ability is typically influenced by several morphological parameters, such as morphology of the locomotor appendices, muscular capacity, body mass, or fluctuating asymmetry, and may differ between sexes and age classes. In this study, we tested the relationship among these variables and jumping performance in 712 Iberian green frogs Pelophylax perezi from an urban population. The results suggest that the main determinant of jumping capacity was body size (explaining 48% of variance). Larger frogs jumped farther, but jumping performance reached an asymptote for the largest frogs. Once controlled by structural body size, the heaviest frogs jumped shorter distances, suggesting a trade-off between fat storage and jumping performance. Relative hind limb length also determined a small but significant percentage of variance (2.4%) in jumping performance—that is, the longer the hind limbs, the greater the jumping capacity. Juveniles had relatively shorter and less muscular hind limbs than adults (for a given body size), and their jumping performance was poorer. In our study population, the hind limbs of the frogs were very symmetrical, and we found no effect of fluctuating asymmetry on jumping performance. Therefore, our study provides evidence that jumping performance in frogs is not only affected by body size, but also by body mass and hind limb length, and differ between age classes.

Effects of canine heartworm (Dirofilaria immitis) on body condition and activity of free-ranging coyotes (Canis latrans)

2000 ◽  
Vol 78 (6) ◽  
pp. 1042-1051 ◽  
Author(s):  
Benjamin N Sacks ◽  
Karen M Blejwas
Keyword(s):  
Body Mass ◽  
Body Condition ◽  
Dirofilaria Immitis ◽  
Canis Latrans ◽  
Infected Group ◽  
Control Group ◽  
Canine Heartworm ◽  
Average Body Mass ◽  
Free Ranging ◽  
Average Body

We used radiotelemetry to study relationships among canine heartworm (Dirofilaria immitis) infection, body condition, and activity of free-ranging coyotes (Canis latrans). Average body mass at death was lower for 17 coyotes in a high-intensity infected group (mean = 33.6 heartworms) than for 18 coyotes in a control group (mean = 3.6 heartworms; p < 0.01). Coyotes in the infected group lost body mass at an average rate of 20% per year relative to the control group (p < 0.01). Bone marrow fat was negatively correlated with heartworm burden (R2 = 0.27; p < 0.01). Average body mass of coyotes at initial capture (i.e., potentially before infection) did not differ between infected and control groups (p = 0.90; 1–β = 0.70). Activity was negatively correlated with heartworm burden during the last 2 months of life (R2 = 0.30; p < 0.01), but no correlation was found 2–4 months before death. Activity of the infected group (n = 13) declined over time (p = 0.01), whereas no difference in activity was observed in the control group (n = 13; p = 0.50). Our findings indicate that heartworm infection reduced body condition and activity of coyotes but that nutritional status did not significantly affect susceptibility to infection.

scholarly journals Does risk of predation influence population dynamics? Evidence from cyclic decline of snowshoe hares

1995 ◽  
Vol 22 (1) ◽  
pp. 115 ◽  
Author(s):  
D. S. Hik
Keyword(s):  
Predation Risk ◽  
Body Mass ◽  
Female Body ◽  
Population Decline ◽  
Control Area ◽  
High Rate ◽  
Food Treatment ◽  
Snowshoe Hares ◽  
Risk Of Predation ◽  
Female Body Mass

Like most heavily preyed-upon animals, snowshoe hares (Lepus americanus) have to balance conflicting demands of obtaining food at a high rate and avoiding predators. Adopting foraging behaviours to minimise predation risk may also lead to a decline in condition, and hence fecundity. Predictions of three hypotheses (condition constraint hypothesis, predator-avoidance constraint hypothesis, predation-sensitive foraging (PSF) hypothesis) were tested by comparing changes in the survival and condition of snowshoe hares on four experimental areas in winter during a cyclic peak and decline (1989–1993) near Kluane Lake, Yukon, Canada, where (i) predation risk was reduced by excluding terrestrial predators (FENCE), (ii) food supply was supplemented with rabbit chow ad libitum (FOOD), (iii) these two treatments were combined (FENCE+FOOD), and (iv) an unmanipulated CONTROL was used. Different pattems of survival and changes in body mass were observed in the presence and absence of terrestrial predators. On the CONTROL area, female body mass and fecundity declined, even though sufficient winter forage was apparently available in all years. A similar decrease in body mass was observed on the FOOD treatment, but only during the third year of the population decline. In contrast, female body mass remained high throughout the decline in the absence of terrestrial predators in the FENCE+FOOD and FENCE treatments. Winter survival declined on CONTROL and FENCE areas during the first year of the population decline (1991), but remained higher on FOOD until 1992 and FENCE+FOOD until 1993. These results generally supported the PSF hypothesis where terrestrial predators were present (CONTROL and FOOD grids). Where terrestrial predators were absent (FENCE and FENCE+FOOD), the results supported the alternative condition constraint hypothesis. The evidence suggests that a cascade of sublethal behavioural and physiological effects associated with increased predation risk contribute to the population decline and delayed recovery of cyclic low-phase populations of snowshoe hares.

Influence of repeated fertilization on forest ecosystems: relative habitat use by snowshoe hares (Lepus americanus)

2006 ◽  
Vol 36 (9) ◽  
pp. 2080-2089 ◽  
Author(s):  
Thomas P Sullivan ◽  
Druscilla S Sullivan ◽  
Pontus MF Lindgren ◽  
Douglas B Ransome
Keyword(s):  
Habitat Use ◽  
Pinus Contorta ◽  
Large Scale ◽  
Lodgepole Pine ◽  
Structural Diversity ◽  
Lepus Americanus ◽  
Volume Index ◽  
South Central ◽  
Crown Volume ◽  
Snowshoe Hares

This study was designed to test the hypothesis that large-scale precommercial thinning (PCT) and repeated fertilization of lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) would enhance relative habitat use by snowshoe hares (Lepus americanus Erxleben) in managed stands. Study areas were located near Summerland, Kelowna, and Williams Lake in south-central British Columbia, Canada. Each study area had nine treatments: four pairs of stands thinned to densities of 250, 500, 1000, and 2000 stems/ha, with one stand of each pair fertilized five times at 2-year intervals, and an unthinned stand. Understory vegetation and relative habitat use by snowshoe hares were measured annually from 1999 to 2003, 6–10 years after the onset of treatments. Mean crown volume index of herbs was significantly higher in fertilized than unfertilized stands, but density had no effect. Shrub volume was not affected by either treatment. Mean crown volume index of trees was significantly greater in the fertilized and high-density stands. Mean total richness of vascular plants was significantly reduced by fertilization. Mean total structural diversity of vegetation was highest in the low-density stands but was not affected by fertilization. Relative habitat use by hares, based on fecal pellet counts, was highest in the 2000 stems/ha and unthinned stands in summer. This pattern also occurred in winter when hare use was higher in fertilized than unfertilized stands. Overall, fertilized 2000 stems/ha stands provided habitat for hares to a degree comparable with unthinned stands of lodgepole pine.

Seasonal Metabolic Acclimatization in a Northern Population of Free-Ranging Snowshoe Hares,Lepus americanus

2009 ◽  
Vol 90 (3) ◽  
pp. 761-767 ◽  
Author(s):  
Michael J. Sheriff ◽  
Louise Kuchel ◽  
Stan Boutin ◽  
Murray M. Humphries
Keyword(s):  
Lepus Americanus ◽  
Northern Population ◽  
Snowshoe Hares ◽  
Free Ranging

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.

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