Effects of mother condition on pregnancy and early losses of calves in semi-domesticated reindeer

• Main Author: Lagergren, Madeleine
• Other Authors: Audun Stien (NINA), Atle Mysterud (UiO), Torkill Tveraa (NINA), Torbjørn Ergon (UiO)
• Format: Master Thesis
• Language: English
• Published: 2011
• Subjects: VDP::470; Norway; Finnmark
• Online Access: http://hdl.handle.net/10852/11869; http://urn.nb.no/URN:NBN:no-27075

A central issue in life history theory is the trade-off between current reproduction and future survival. As mammalian herbivores with long life prioritize survival above reproduction, especially under harsh conditions, reproductive rates can be relatively variable and low in years with poor food availability. The aim of this study was to get a better understanding of how reproduction outputs were affected by mothers’ condition in a large herbivore, and how environmental conditions may affect this relationship. Demographic data on female body masses, ages, pregnancy rates and early calf survival was collected in a semi-domesticated reindeer herd in Finnmark, Norway, during 2010. In addition, the data collected was compared with previous studies from two years with very different climatic conditions. I expected pregnancy rates and early calf survival to depend on female condition and/or age, and that the female condition and/or age dependent calf survival was associated with delayed calving and small calf body masses at birth. I also expected that a year with unfavorable climatic conditions would be characterized by very low reproductive success due to mothers favouring own survival over reproduction. The probability of pregnancy was strongly dependent on female age, with no calves being pregnant, a low proportion of yearlings being pregnant, while almost all the adult females (2 year or older) were pregnant. Only in the yearling age group was there a relationship between pregnancy rates and female body mass. The probability of miscarriages and early calf survival depended mainly on female age; yearlings were much more likely to loose their calf than adult females. These lower rates among yearlings may suggest that yearlings give priority to own somatic growth over current reproduction. In addition, little maternal experience may increase calf mortality rates in yearlings, as they all were primiparous. Early calf survival was independent of female condition in this study. One reason for the lack of a female ...