Does body condition affect fecundity in a cyclic population of snowshoe hares?

1999 ◽  
Vol 77 (1) ◽  
pp. 1-6 ◽  
Author(s):  
Karen E Hodges ◽  
Carol I Stefan ◽  
Elizabeth A Gillis
Keyword(s):  
Predation Risk ◽  
Body Condition ◽  
Age Structure ◽  
Lepus Americanus ◽  
Decline Phase ◽  
Skeletal Size ◽  
Nutritional Deficit ◽  
Snowshoe Hares ◽  
Cyclic Changes ◽  
Cyclic Fluctuation

Snowshoe hares (Lepus americanus) undergo a 10-year cycle in abundance, with cyclic changes in reproduction occurring 3 years prior to numeric changes. Reproduction may be associated with body condition, which might change with nutrition or predation pressure. We describe hare body condition (as a mass - skeletal size relationship) through a cycle in the southern Yukon from 1989 to 1996, test the effects of food and predation risk on body condition, and examine whether changes in body condition are related to cyclic reproductive changes. Hare body condition was lowest during the decline phase but rapidly improved during the low phase. Although yearling hares were in poorer condition than adults, changes in age structure cannot explain the cyclic fluctuation in condition. Food addition and predator reduction both resulted in better body condition. Body condition did not affect reproduction. The highest natality occurred when hares were in intermediate condition, while the lowest natality occurred when hares were in the best condition. Although changes in food and predation risk affect hare body condition, we found no relationship between body condition and cyclic reproductive changes. Rather, during times of nutritional deficit, female hares may maintain mass during gestation and lactation, but at a proximate cost to their offspring. Thus, inferences based on indices of condition incorporating body mass may be misleading.

scholarly journals Glucocorticoids, state-dependent reproductive investment and success in the face of danger in a long-lived bird

2020 ◽  
Author(s):  
Kristina Noreikienė ◽  
Kim Jaatinen ◽  
Benjamin B. Steele ◽  
Markus Öst
Keyword(s):  
Predation Risk ◽  
Telomere Length ◽  
Clutch Size ◽  
Body Condition ◽  
Nest Predation ◽  
Hatching Success ◽  
Reproductive Investment ◽  
Trade Off ◽  
Relative Telomere Length ◽  
Future Reproduction

AbstractGlucocorticoid hormones may mediate trade-offs between current and future reproduction. However, understanding their role is complicated by predation risk, which simultaneously affects the value of the current reproductive investment and elevates glucocorticoid levels. Here, we shed light on these issues in long-lived female Eiders (Somateria mollissima) by investigating how current reproductive investment (clutch size) and hatching success relate to faecal glucocorticoid metabolite [fGCM] level and residual reproductive value (minimum years of breeding experience, body condition, relative telomere length) under spatially variable predation risk. Our results showed a positive relationship between colony-specific predation risk and mean colony-specific fGCM levels. Clutch size and female fGCM were negatively correlated only under high nest predation and in females in good body condition, previously shown to have a longer life expectancy. We also found that younger females with longer telomeres had smaller clutches. The drop in hatching success with increasing fGCM levels was least pronounced under high nest predation risk, suggesting that elevated fGCM levels may allow females to ensure some reproductive success under such conditions. Hatching success was positively associated with female body condition, with relative telomere length, particularly in younger females, and with female minimum age, particularly under low predation risk, showing the utility of these metrics as indicators of individual quality. In line with a trade-off between current and future reproduction, our results show that high potential for future breeding prospects and increased predation risk shift the balance toward investment in future reproduction, with glucocorticoids playing a role in the resolution of this trade-off.

The impact of variable predation risk on stress in snowshoe hares over the cycle in North America’s boreal forest: adjusting to change

Oecologia ◽  
2021 ◽  
Author(s):  
Sophia G. Lavergne ◽  
Charles J. Krebs ◽  
Alice J. Kenney ◽  
Stan Boutin ◽  
Dennis Murray ◽  
...  
Keyword(s):  
Boreal Forest ◽  
Predation Risk ◽  
Snowshoe Hares ◽  
The Impact

Food supplementation and predation risk in harsh climate: interactive effects on abundance and body condition of tit species

Oikos ◽  
2016 ◽  
Vol 126 (6) ◽  
pp. 863-873 ◽  
Author(s):  
Chiara Morosinotto ◽  
Alexandre Villers ◽  
Rauno Varjonen ◽  
Erkki Korpimäki
Keyword(s):  
Predation Risk ◽  
Body Condition ◽  
Interactive Effects ◽  
Food Supplementation ◽  
Harsh Climate

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.

EFFECT OF THE COW'S BODY CONDITION AND STAGE OF LACTATION ON DEVELOPMENT OF MILK RANCIDITY1

1970 ◽  
Vol 33 (8) ◽  
pp. 339-342 ◽  
Author(s):  
M. J. Ortiz ◽  
E. M. Kesler ◽  
G. H. Watrous ◽  
W. H. Cloninger
Keyword(s):  
Body Condition ◽  
Milk Fat ◽  
Body Condition Score ◽  
Sampling Period ◽  
Milk Samples ◽  
Stage Of Lactation ◽  
Skeletal Size ◽  
Milk Flow ◽  
Condition Score ◽  
The Times

An objective of this study was to investigate the relationship between body condition of the dairy cow and susceptibility of milk to rancidity. Initial milk samples were obtained from 166 cows in Spring, 1969, and all animals were retested after an interval of two months. Additional observations included the effects of stage of lactation, level of milk production, and herd effects. Each cow was evaluated for body condition, at the times when milk samples were obtained, by a method based on measures of weight and skeletal size and by a subjective scoring system. Spontaneous rancidity of the milk fat was allowed to develop upon storage for 48 hr; and induced rancidity was brought about by controlled agitation. As measured by acid degree values (ADV) the treatments imposed on the milk samples were successful in simulating development of spontaneous and induced lipolysis of the milk fat. However, the magnitude of the ADV was not related to body condition score. It is concluded that in well-fed herds, such as those used in this experiment, body condition of the cow does not influence the susceptibility of her milk to rancidity. These data may not apply under conditions of poor feeding and management. Advancing stage of lactation was associated with increases in both spontaneous and induced rancidity. This was indicated by positive correlations between days in milk and ADV, and by significantly higher values in the second sampling period than in the first. There was a negative correlation between the amount of milk produced and ADV. This may have been related to the decline in milk flow which accompanied advancing lactation. An unexplained herd difference existed with respect to the susceptibility of milk to induced rancidity.

Reproductive changes in a cyclic population of snowshoe hares

2001 ◽  
Vol 79 (11) ◽  
pp. 2101-2108 ◽  
Author(s):  
Carol I Stefan ◽  
Charles J Krebs
Keyword(s):  
Pregnancy Rate ◽  
Breeding Season ◽  
Litter Size ◽  
Reproductive Output ◽  
Yukon Territory ◽  
The Body ◽  
Decline Phase ◽  
Snowshoe Hares ◽  
Early Increase ◽  
Changes In Pregnancy

Reproductive output was estimated for a cyclic population of snowshoe hares (Lepus americanus) in the Kluane Lake region of the southwest Yukon Territory. Data collected by five researchers were collated over 8 years (1989–1996). Pregnant hares were captured and held in cages until they gave birth so that reproductive characteristics could be measured. Pregnancy rate, litter size, and neonate size fluctuated significantly throughout the cycle, changes occurring about 2 years before corresponding changes in density. Pregnancy rates were nearly 100% early in the breeding season, but declined up to 20% in the last gestation periods of the year. The number of litters produced in a breeding season varied between two (decline phase) and four (low, early increase phase). Litter size varied among years as well as among litters within a year, larger litters being born later in the breeding season. The body mass and size of newborn hares varied by 5–33% among years. The combined changes in pregnancy rate and litter size resulted in a cyclic change in total reproductive output ranging from a low of 6.9 young per female during the decline phase to a maximum of 18.9 during the second year of the low and early increase phases.

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