Natural parasites in conjunction with behavioral and color traits explain male agonistic behaviors in a lizard

Male competition conforms to a cost-benefit model,because while aggression may increase reproductive prospects,it can also increase the risk of injury.We hypothesize that an additional cost in aggressive males would be an increase in parasite load associated with a high energy investment into sexual competition.Some of these infections,in turn,may downmodulate the level of host aggression via energetic trade-offs.We staged dyadic male contests in the lab to investigate the relationships of multiple parasites with the agonistic behavior of lizard hosts,Sceloporus occidentalis.We also included both color and behavioral traits from opponents in the analyses because(1)color patches of lizards may serve as intraspecific signals used by conspecifics to assess the quality of opponents,and(2)contests between male lizards fit classical models of escalated aggression,where lizards increase aggression displays in response to an opponent's behavior.The results conform to our hypothesis because male lizards displayed more pushups when they had more ticks.Moreover,some parasites may modulate the levels of aggression because lizards infected by hematic coccidians performed fewer pushups.Interestingly,lizards also displayed fewer pushups when both the chroma and size of the opponent's blue patch were greater.The results thus also supported the role of the blue patch of s.occidentalis as a sexual armament,because it contributed to the deterrence of aggression from opponent lizards.We revealed that natural parasitic infections in lizard hosts can contribute to their agonistic behavior.We encourage future studies to account for parasites in behavioral testswithlizards.

Differential effects of environmental climatic variables on parasite abundances in blue tit nests during a decade

Models on climate change have predicted an increase of temperature over the earth’s surface with potential drastic effects on living organisms.We analyzed the relationships between climatic conditions(temperature,rainfall,and wind speed)and the abundance of blood-sucking flying insects(biting midges and blackflies)and nest-dwelling ectoparasites(mites,fleas,and blowflies)collected from blue tit nests during bird breeding seasons for a period of 10 years.Average temperature,rainfall,and wind speed showed significant differences among years.Temperature and wind speed increased during the period of study while rainfall decreased.Biting midge,blackfly,and blowfly abundances increased across years but not flea and mite abundances.Hatching date decreased and brood size increased across years.Independently of year variation,parasites were related to climatic variables.For example,biting midge,blowfly,mite,and flea abundances were positive and significantly related to average temperature.We also found a positive and significant relationship between abundances of Haemoproteus infections and biting midge abundances during the first year of life of birds out of nests.However,abundance and prevalence of Lankesterella infections in yearlings were positive and significantly related to mite abundances during the year of birth of birds.Leucocytozoon and Lankesterella infections were also significantly related to climatic variables and Haemoproteus and Lankesterella infections increased across years.In addition,body condition of adult females and males were negatively related to flea larvae and blowfly abundance respectively.Nestling body condition was also negatively related to biting midge abundance.Changes in climatic conditions across years could therefore affect several parasites of birds but also to birds themselves.