Are animals shrinking due to climate change? Temperature-mediated selection on body mass in mountain wagtails.

Climate change appears to affect body size of animals whose optimal size in part depends on temperature. However, attribution of observed body size changes to climate change requires an understanding of the selective pressures acting on body size under different temperatures. We examined the link between temperature and body mass in a population of mountain wagtails (Motacilla clara) in KwaZulu-Natal, South Africa, between 1976 and 1999, where temperature increased by 0.18 [Formula: see text]C. The wagtails became lighter by 0.035 g per year. Partitioning this trend, we found that only a small part of the effect (0.009 g/year) was due to individuals losing weight and a large part (0.027 g/year) was due to lighter individuals replacing heavier ones. Only the latter component was statistically significant. Apparently, the wagtails were reacting to selection for reduced weight. Examining survival, we found that selection was temperature-mediated, i.e., lighter individuals survived better under high temperatures, whereas heavier individuals survived better under low temperatures. Our results thus support the hypothesis that temperature drove the decline in body mass in this wagtail population and provides one of the first demonstrations of the selective forces underlying such trends.

The individualisation of a dog bite mark: a case study highlighting the bite mark analysis, with emphasis on differences between dog and human bite marks.

A person who keeps or controls a dog in his own interest is liable "without fault" should that dog cause harm to any person. By owning a dog, man welcomes into his home a beast that preserves much of its primordial self, and is capable of inflicting a fatal bite wound. The courts may require the forensic expert to identify which specific dog caused the damage or fatal bite in an effort to establish the owner/controller of the animal. Very little has been published on the individualisation of dog bite marks, the procedures to be followed when confronted with usable bite marks and the range of analysis techniques available. The authors advocate a multidisciplinary approach, and utilise a case study to demonstrate the protocol to be followed when analysing a dog bite mark. The paper also highlights differences between human and dog inflicted bites. The authors warn against over interpretation of poor quality bite marks and a final conclusion of absolute certainty.