Resembling a Viper: Implications of Mimicry for Conservation of the Endangered Smooth Snake

The phenomenon of Batesian mimicry, where a palatable animal gains protection against predation by resembling an unpalatable model, has been a core interest of evolutionary biologists for 150 years. An extensive range of studies has focused on revealing mechanistic aspects of mimicry (shared education and generalization of predators) and the evolutionary dynamics of mimicry systems (co‐operation vs. conflict) and revealed that protective mimicry is widespread and is important for individual fitness. However, according to our knowledge, there are no case studies where mimicry theories have been applied to conservation of mimetic species. Theoretically, mimicry affects, for example, frequency dependency of predator avoidance learning and human induced mortality. We examined the case of the protected, endangered, nonvenomous smooth snake (Coronella austriaca) that mimics the nonprotected venomous adder (Vipera berus), both of which occur in the Åland archipelago, Finland. To quantify the added predation risk on smooth snakes caused by the rarity of vipers, we calculated risk estimates from experimental data. Resemblance of vipers enhances survival of smooth snakes against bird predation because many predators avoid touching venomous vipers. Mimetic resemblance is however disadvantageous against human predators, who kill venomous vipers and accidentally kill endangered, protected smooth snakes. We found that the effective population size of the adders in Åland is very low relative to its smooth snake mimic (28.93 and 41.35, respectively).Because Batesian mimicry is advantageous for the mimic only if model species exist in sufficiently high numbers, it is likely that the conservation program for smooth snakes will fail if adders continue to be destroyed. Understanding the population consequences of mimetic species may be crucial to the success of endangered species conservation. We suggest that when a Batesian mimic requires protection, conservation planners should not ignore the model species (or co‐mimic in Mullerian mimicry rings) even if it is not itself endangered. Implications of mimicry for Conservation of the endangered smooth snake     

Are nest characters of importance when choosing a male in the fifteen-spined stickleback (Spinachia spinachia)?

Male fifteen-spined sticklebacks (Spinachia spinachia) build their nests by wrapping epiphytic algae around macroalgae and securing them with secretional threads. In this study, I show that female fifteen-spined stickleback prefer males which have built their nests above the surrounding vegetation. High-located nests are safer, because they are less likely to attract egg-predators such as shore crabs (Carcinus maenas). Thus, I found that shore crabs more rapidly find eggs in nests built close to the bottom than in nests well above the it. Moreover, male-male competition could be an additional explanation as to why males build nests high up. Thus, my field results suggest that the closer the males were to a neighbour, the higher they built. Larger males were also found to have larger territories but male size did not correlate with the height of the nest above the surrounding vegetation. Females showed no preference for nest size, regardless of the presence of egg-predators. However, they tended to choose nests that had no egg-predators in the vicinity over nests with egg-predators close by. Female choosiness for certain nest characters may provide one explanation for the evolution of male care in this species. Received: 29 December / 1999 Revised: 18 April 2000 / Accepted: 28 May 2000     

Effect of maternal dietary hexachlorocyclohexane exposure on pup survival and growth in albino rats

Abstract

In adult albino rats, maternal dietary. ß‐ and ?‐hexachlorocyclohexane (HCH) intake during gestation upto 400 ppm level did not affect the number of litters produced. But about 50 and 100% pup mortality was found in 200 and 400 ppm ß ‐HCH group within 5 days of birth. Maternal mortality was observed in 800 ppm ß ‐HCH group during third week of gestation. The effect of maternal dietary intake of HCH isomers at 50 and 250 ppm level during gestation and/or lactation on perinatal development was also studied. The body weights and sizes of the newborn litters of mother rats exposed to dietary HCH isomers did not. differ from controls. Similarly, the growth and development of the litters of HCH exposed mother rats that survived 28 day lactation period were found to be comparable to controls as evidenced by the body weight and weight of vital organs. However, liver weight increases were found in the 28 day weaned litters wherever the mothers had been exposed to HCH isomers during lactation. Lowered kidney weight was seen in litters of mother rats fed 250 ppm ?‐HCH during gestation and lactation. The brain and testis weights were not affected in the litters of any experimental groups.     

Ploidy-, gender-, and dose-dependent alteration of selected biomarkers in Clarias gariepinus treated with benzo[a]pyrene

Naturally-occurring and artificially-induced polyploids have been documented in various fish species but to date no comparison has been reported of the impacts of ploidy on fish biomarker responses to organic pollutants. This study describes effects of ploidy, gender, and dose on biliary fluorescent aromatic compound (FAC) concentrations, hepatic ethoxyresorufin-O-deethylase (EROD) and glutathione S-transferase (GST) activities in one of the most commonly cultured warm-water species, the African catfish Clarias gariepinus. Recently matured male and female diploid and triploid fish were intraperitoneally (i.p.) injected with 0, 5 or 25 mg/kg benzo[a]pyrene (BaP) and liver and gallbladder were sampled 48 hr later. No significant differences were found between ploidies in bile concentrations of 7,8 dihydrodiolbenzo[a]pyrene (7,8D BaP), 1-hydroxybenzo[a]pyrene (1-OH BaP) or 3-hydroxybenzo[a]pyrene (3-OH BaP). However, concentrations of the biliary FACs did differ between males and females at different dose of injection with generally higher concentrations in females at the low dose of BaP and higher concentrations in males at the higher BaP concentration. Hepatic EROD activity did not exhibit gender-dependent difference, whereas it was significantly higher in triploids than diploids. GST activities were not significantly influenced by any of the tested factors. This work advanced our understanding of the role of ploidy, gender, and dose in biotransformation of pollutants in fish.     

Culturally correct song dialects are correlated with male age and female song preferences in wild populations of brown-headed cowbirds

Variation in vocal behavior among local populations of songbirds may be significant to females in mate choice. In a study of dialect populations of brown-headed cowbirds, estradiol-implanted females from two dialects held the pre-copulatory lordosis posture longer in response to playback of the local flight whistle song than to foreign whistle types from adjacent and more distant dialects. Females were held in captivity for a relatively brief period prior to testing and received no tutoring so discrimination was based solely on experience in the wild. This is the first study to show evidence of discrimination by female cowbirds based on flight whistle type. Evidence is presented from one of the study dialects that the majority of yearling male cowbirds are vocally distinct from resident adults in having either foreign or incomplete local whistles. Although these yearlings are fully mature sexually, they have little or no mating success. The correlation between female whistle preference and male mating success suggests that the ability to give the correct local whistle type may be a characteristic used by females to assess age and quality of a potential mate. A learned female preference for the predominant local song type may be a factor in the stability of these dialects by making it adaptive for males to conform to the local dialect.     

Female sex pheromone in immature insect males—a case of pre-emergence chemical mimicry?

Sexual selection by competition for mates is a formidable force that has led to extraordinary adaptations in males. Here we present results suggesting a novel case of pheromone mimicry in males of Lariophagus distinguendus, a parasitic wasp of beetle larvae that develop in stored grain. Females of L. distinguendus produce a pheromone even before they emerge from a grain. Males are attracted to the parasitised grain and wait for females to emerge. Males emerging later than others are under enormous selection pressure since females mate only once. We show evidence that developing males fool their earlier emerging competitors by mimicking the female pheromone. Males exposed to pupae of either sex exhibit typical courtship behaviour. Searching males are not only arrested by grains containing developing females but spend as much time on grains containing developing males. Hence, by distracting their competitors away from receptive females late males may increase their own chance to mate with these females. After emergence, males decompose the active compounds within 32 h probably to decrease molestation during their own search for mates. Chemical analyses of active pheromone extracts and bioassays using fractions demonstrate that the active compounds are among the cuticular hydrocarbons.     

Solitary nesting as an alternative breeding tactic in colonial nesting bluegill sunfish (Lepomis macrochirus)

Colonial breeding can evolve in response to benefits afforded by clumped individuals, such as reduced predation and increased ease of assessing potential mates. However, colonial breeding can also impose costs such as increased disease transmission or increased cuckoldry. Here, we investigate solitary nesting as a potential alternative breeding tactic in colonial breeding bluegill sunfish (Lepomis macrochirus). Most male bluegill, termed parentals, compete for nesting sites in colonies and then court and spawn with females and provide sole care of the eggs. Although nesting in a colony results in reduced predation and fungal infection of broods, it comes at a cost of increased parasitism by specialized cuckolder males that do not nest. We found that 4.5% of parentals forgo spawning in a colony and instead construct nests solitarily. Solitary males were of similar size and age to colonial males, but were in significantly better condition. Solitary males obtained as many eggs as males nesting in the center of colonies, and significantly more than males nesting on the periphery of colonies. Thus, females do not appear to discriminate against solitary males. Solitary males had smaller ear tabs, a presumed sexually selected character used by parental males in intrasexual competition, than colonial males. Tracking data revealed consistency in nesting tactic (but not nest position within the colony) between spawning attempts. We suggest that solitary nesting represents either a facultative decision made by parental males in top condition at the onset of breeding, or a life history decision to forgo spawning in colonies.Communicated by K. Lindström     

Female choice on male quantitative traits in lizards — why is it so rare?

Female choice on the basis of male traits has been described in an array of taxa but has rarely been demonstrated in reptiles. In the sand lizard (Lacerta agilis), and possibly in other non-territorial reptiles, a male's contribution to a female's fitness is restricted to his genes. In order to choose males of high genetic quality, females have to trade the fitness gain against the costs of active choice. In a Swedish population of sand lizards, long-lived males sired offspring with higher embryonic survival compared to offspring sired by short-lived males. In spite of this female sand lizards did not mate selectively with older and/or larger males. There appeared to be mo reliable cues to male longevity; age-specific male body size was highly variable. Furthermore, estimates of male nuptial coloration did not covary with ectoparasite load and, hence, females cannot use male coloration as a cue to heritable resistance to pathogenic parasite effects. When cues to male genetic quality are poor, or inaccurate, and males make no parental investment, we predict that female choice will be rare. Sand lizard females mating with many partners lay clutches with higher hatching success. Thus, females may obtain good genes for their young by multiple mating, thereby avoiding costs associated with mate choice.     

Mate sampling behaviour of black grouse females (Tetrao tetrix)

We studied female mate sampling behaviour in lekking black grouse (Tetrao tetrix). Females mainly visited males occupying territories in the centre of the lek with relatively large territories. They were also more likely to visit males that had high attendance. The same factors were also correlated with male mating success. A multiple regression model including these factors explained more of the variance in female visits per male (53%) than in mating success (33%). The pattern of female sampling conformed with a pool comparison (best-of-n) tactic. Such a tactic is expected if the costs of sampling are low. Females of high body mass visited more males than lighter females, however, which indicates that females may vary in their search tactics and suggests that there may be search costs. The existence of costs is further suggested by the fact that if the mate from a previous year was still present, females always mated with the same male in the following year. Though search costs were not measured directly, our findings suggest that some costs are negligible (e.g. energetic exhaustion or predation) whereas others (timing of mating) may be more important.     

Preparation and activation: determinants of age at reproductive maturity in male baboons

Age at maturity is a particularly important life history trait, but maturational data are rare for males in natural populations of mammals. Here we provide information on three maturational milestones and their social and demographic correlates among 43 wild male baboons, Papio cynocephalus, in a natural population in Amboseli National Park, Kenya. We examined (1) age at testicular enlargement, which signals puberty and the onset of subadulthood, (2) age at attainment of adult dominance rank, which we consider to be the beginning of adulthood, and (3) age at first sexual consortship, which is the best measure available for age at first reproduction in male baboons. Testicular enlargement (median age = 5.69 years) occurred earlier among sons of high ranking mothers, and was not influenced by rainfall or seasonality. Attainment of adult dominance rank (median age = 7.41 years) was also accelerated among sons of high-ranking mothers, and among males whose mothers had died while the males were juveniles. First sexual consortship (median age = 7.92 years) was not influenced directly by maternal characteristics, but attainment of adult dominance rank always preceded first consortship. The lag time between attainment of adult rank and first consortship (median = 2.5 months; range = 5–526 days), was predicted by the number of sexually cycling females in the group when the male attained rank, and by how high ranking the male became in his first months as an adult. We suggest that the age at which a male baboon is ready to begin reproducing is influenced by a relatively stable maternal characteristic that exerts its influence early in development, but the timing with which this potential is realized depends on activation by more proximate, often stochastic triggers such as female availability. This two-level organization of influences is likely to contribute to the variance both in age at first reproduction and in lifetime fitness. Differences in the relative magnitude of the two levels will lead to both intra- and interspecific variability in the opportunity for maternal selection and sexual selection.