The cost of maturing early in a solitary carnivore

Abstract

Central to the theory of life history evolution is the existence of trade-offs between different traits, such as the trade-off between early maturity and an extended period of body growth. Based on analysis of the reproductive tracts of harvested Eurasian lynx (Lynx lynx) females in Norway, we find that females that mature early are generally heavier than those that postpone maturation. A higher proportion of 1.5-year-old females showed signs of ovulation in areas with high prey density, where they were also heavier. Further, we show that female Eurasian lynx that mature early have the same number of placental scars (an index of breeding investment and litter size) as older females, suggesting that they have a relatively high investment in their first litter. This induces a cost in terms of body weight development, as those females that had matured at the age of 1.5 years were substantially lighter by the age of 2.5 years than those that postponed breeding. This effect tended to be more pronounced in areas with low prey density. We discuss to what extent this might affect their future fitness prospects, and suggest that such costs of maturing early in terms of body weight development might be high in terrestrial large carnivores due to a prolonged period of postnatal care.

Patterns of variation in reproductive parameters in Eurasian lynx (Lynx lynx)

“…In general the breeding proportion was highest in the southernmost study population (Bergslagen), and lowest in the northernmost population (Sarek), with both the Norwegian populations showing intermediate values. Supporting these findings, we have previously found that the proportion of 1.5-year-old females that ovulate (i.e., that are sexually mature) was generally lower in the northernmost areas (Nilsen et al 2010). Consequently, on a broad scale the patterns might indicate a slower life cycle in more extreme northern environments.…”

“…While there was a clear difference between females that were 2 years old and those that were older in the proportion that gave birth, litter sizes did not differ between these age classes, indicating that females that mature early invest relatively heavily in their first litter (see also Nilsen et al 2010). This might be somewhat surprising given the potentially high costs of reproduction at low age in carnivores (Proaktor et al 2007).…”

“…Consequently, on a broad scale the patterns might indicate a slower life cycle in more extreme northern environments. Previous studies on lynx have indicated a clear effect of body mass on age at maturity (Nilsen et al 2010). It is therefore possible that different maturation rates between sites will result in differential allocation to reproduction among yearling lynx in the different study areas (restraint hypothesis; Curio 1983), due to different growth rates affecting patterns of maturation in the populations.…”

“…It is therefore possible that different maturation rates between sites will result in differential allocation to reproduction among yearling lynx in the different study areas (restraint hypothesis; Curio 1983), due to different growth rates affecting patterns of maturation in the populations. Although speculative, the different patterns in breeding proportions assessed by litter size observations and ovulation rates reported by Nilsen et al (2010) suggest that the geographical variation in the breeding proportion may be caused by differences in feeding conditions and growth rates among areas. This theory is supported by the fact that body size and body mass of lynx in southern Sweden were related to roe deer availability during the first year of life (Yom-Tov et al 2010).…”

Quota hunting of Eurasian lynx in Norway: patterns of hunter selection, hunter efficiency and monitoring accuracy

“…In response to this, separate female quotas in the lynx harvest have been allocated since the late 1990s in Norway. Although considerable effort has been spent in studying lynx ecology in Norway (Andrèn et al 2006;Nilsen et al 2010;Nilsen et al 2009;Odden et al 2006), so far little is known about the magnitude and composition of the harvest, and even less is known about the bag composition in relation to the standing population structure (Saether et al 2010).…”