Calving success of female caribou in relation to body weight

Abstract

In late September and October 1987–1990 and early July 1988–1991, 66 radio-collared female caribou (Rangifer tarandus granti) of the Central Arctic Herd were captured and weighed 117 times. Caribou were relocated repeatedly during early June 1988–1991; parturition status, calving date, and perinatal calf survival were determined. Mean autumn body weights of subsequently parturient (90.0 kg) and nonparturient (82.5 kg) females differed significantly (P < 0.01). Mean summer weights 4 – 5 weeks after parturition were significantly higher for females that had calved on or before 7 June (82.2 kg) than for those that had calved after 7 June (72.1 kg; P < 0.01), and for females whose calves survived at least 2 days post partum (80.2 kg) than for those whose calves died within 2 days (70.3 kg; P < 0.01). Significant logistic models were generated for relationships between parturition rate and autumn weight (P < 0.01), between the occurrence of early calving and summer weight (P < 0.05), and between calf survival rate and summer weight (P < 0.02). Body weight appears to be a reasonable index of body condition, which in turn is related to reproductive performance. The probability of a successful pregnancy is largely predetermined at breeding, based on autumn condition, whereas calving date and early calf survival appear to be influenced primarily by maternal condition during late pregnancy.

Using movement behaviour to define biological seasons for woodland caribou

“…In terms of annual variation, over three years peak onset varied by up to 20 days for winter, although only 4-5 days for spring and calving. These findings, particularly with respect to calving, corroborate with what has been documented elsewhere for woodland caribou (Bergerud, 1975;Ferguson & Elkie, 2004), barren-ground caribou (Cameron et al, 1993;Post & Klein, 1999), and Eurasian reindeer (Eloranta & Nieminen, 1986;Flydal & Reimers, 2002).…”

“…Calving, for example, is a relatively predictable biological event that tends to be well defined for populations based on field observations (Rettie & Messier, 2001). Despite this, the peak onset of calving can vary annually by as much as 15 days (Eloranta & Nieminen, 1986;Cameron et al, 1993;Post & Klein, 1999;Flydal & Reimers, 2002). Furthermore, calving times for individuals within a population may vary by as much as a month or more (Bergerud, 1975;Eloranta & Nieminen, 1986;Post & Klein, 1999;Ferguson & Elkie, 2004).…”

Using ultrasound measurements of rump fat to assess nutritional condition of woodland caribou in northern British Columbia, Canada

“…Nutritional condition is the state of body components for an individual that may influence current and/or future fitness (Harder & Kirkpatrick, 1994). Therefore, it affects the reproductive capacity of a population (Adams & Dale, 1998a,b;Albon et al, 1986;Cameron et al, 1993;Cameron & Ver Hoef, 1994;Heard et al, 1997;Ouellet et al, 1997) and may provide insights into the quality of habitats that animals occupy (Stephenson et al, 2002). Body condition may also affect appetite (Boertje, 1990) which could alter the levels of predation risk within foraging strategies (Stephens & Krebs, 1986).…”

Growth and body weight of free-range reindeer in western Alaska

“…Body weight of adult females in Rangifer influences conception rates (Dauphine, 1976;Ropstad et al, 1991;, calving time (Reimers, 1983;Cameron et al, 1993), birth weights (Skogland, 1984), recruitment rate (Skogland, 1986;Post & Klein, 1999), and age at first reproduction (Leader-Williams & Rosser, 1983;Langvatn et al, 1996;. As population densities increase, a decline in growth rate and body weight (Skogland, 1983) will affect maximum sustained yield (Karter & Dieterich, 1989;, and may indicate changes in range quality (Fox, 1999).…”