Helper response to experimentally manipulated predation risk in the cooperatively breeding cichlid Neolamprologus pulcher

Background We manipulated predation risk in a field experiment with the cooperatively breeding cichlid Neolamprologus pulcher by releasing no predator, a medium- or a large-sized fish predator inside underwater cages enclosing two to three natural groups. We assessed whether helpers changed their helping behaviour, and whether within-group conflict changed, depending on these treatments, testing three hypotheses: ‘pay-to-stay’ PS, ‘risk avoidance’ RA, or (future) reproductive benefits RB. We also assessed whether helper food intake was reduced under risk, because this might reduce investments in other behaviours to save energy. Methodology/Principal Findings Medium and large helpers fed less under predation risk. Despite this effect helpers invested more in territory defence, but not territory maintenance, under the risk of predation (supporting PS). Experimentally covering only the breeding shelter with sand induced more helper digging under predation risk compared to the control treatment (supporting PS). Aggression towards the introduced predator did not differ between the two predator treatments and increased with group member size and group size (supporting PS and RA). Large helpers increased their help ratio (helping effort/breeder aggression received, ‘punishment’ by the dominant pair in the group) in the predation treatments compared to the control treatment, suggesting they were more willing to PS. Medium helpers did not show such effects. Large helpers also showed a higher submission ratio (submission/ breeder aggression received) in all treatments, compared to the medium helpers (supporting PS). Conclusions/Significance We conclude that predation risk reduces helper food intake, but despite this effect, helpers were more willing to support the breeders, supporting PS. Effects of breeder punishment suggests that PS might be more important for large compared to the medium helpers. Evidence for RA was also detected. Finally, the results were inconsistent with RB.

[Prevalence of heart murmurs, aortic and pulmonic stenosis in boxers presented for pre-breeding exams in Switzerland]

Boxer are predisposed to subaortic (SAS) and pulmonic stenosis (PS). To decrease the prevalence, pre-breeding cardiologic exams were performed in the last years. In our study the results of 309 pre-breeding exams of boxers presented between 1999 and 2008 were evaluated retrospectively. The overall prevalence of heart murmurs was 26.5 %. A SAS was diagnosed in 25 (8.1 %) and a PS in 10 (3.3 %) dogs. A combination of both defects was found in 7 (2.3 %) Boxers. Animals with a heart murmur of at least grade 3/6 had a significantly higher peak aortic flow velocity (VmaxAo) than animals without or only soft heart murmurs. Over the study period both the frequency of heart murmurs and diagnosis of SAS and PS decreased.