Ryan Earley | University of Alabama - Tuscaloosa (original) (raw)
Papers by Ryan Earley
Physiology & behavior, Jan 19, 2015
Reception of pheromone cues can elicit significant physiological (e.g. steroid hormone levels) ch... more Reception of pheromone cues can elicit significant physiological (e.g. steroid hormone levels) changes in the recipient. These pheromone-induced physiological changes have been well documented for male-female interactions, but scarcely in same-sex interactions (male-male and female-female). We sought to address this dearth in the current literature and examine whether mangrove rivulus fish (Kryptolebias marmoratus) could detect and, ultimately, mount a physiological response to the pheromone signature of a potential, same-sex competitor. We examined steroid hormone levels in mangrove rivulus exposed to one of three treatments: 1) isolation, 2) exposure to pheromones of a size-matched partner, and 3) pheromone exposure to a size-matched opponent followed by a physical encounter with the opponent. We found that exposure to a competitor's pheromone cues elicited a significant increase in testosterone levels. Increases in testosterone were similar across genetically distinct lineage...
Animal Behaviour, 2014
ABSTRACT Prior contest experiences can predictably alter an individual's contest performa... more ABSTRACT Prior contest experiences can predictably alter an individual's contest performance and probability of contest success. Although winner and loser effects have been well studied across many animal taxa, the mechanisms underlying these effects and their adaptive value currently are topics of intense interest. Two predominant hypotheses posit that contest experiences alter either an individual's perceived fighting ability or its actual fighting ability. We addressed these hypotheses, and potential physiological and behavioural mechanisms driving experience effects in the green anole lizard, Anolis carolinensis. Prior losers went on to lose a significant proportion of future contests while prior winners were equally likely to win or lose against size-matched opponents. Further analysis revealed that the loser effect arose as a result of individuals updating their perceived fighting ability following a loss. Both prior losing and winning experiences influenced future contest performance with prior losers decreasing and prior winners increasing their aggressiveness in subsequent contests. Status-dependent changes in metabolic physiology were not associated with the presence of the observed loser effect. However, contest status and contest performance interacted to influence metabolic physiology. Plasma glucose concentrations decreased as a function of the frequency of high-risk, escalated behaviours performed by eventual losers, and muscle lactate concentrations increased as a function of the frequency of low-risk threat displays performed by eventual winners. Our results support the notion that prior contest experiences influence an individual's perceived, not actual, fighting ability and that status-dependent changes in metabolic physiology are not a likely mechanism underlying the presence/magnitude of experience effects.
Herpetological Monographs, 2009
We studied the spatial and reproductive ecology of a population of Copperheads (Agkistrodon conto... more We studied the spatial and reproductive ecology of a population of Copperheads (Agkistrodon contortrix), a North American pitviper, in a basalt trap-rock ecosystem in the central Connecticut River Valley, a region that constitutes the northeastern extreme of this species' geographic range. Adult males (n 5 20) and females (n 5 15) were surgically implanted with radio-transmitters and tracked every 48 h during the active season (April through October) for three consecutive years (2001 to 2003). From late autumn to early spring (November through March), when snakes were hibernating and thus inactive, tracking was reduced to once per week. We generated data on movement and other spatial parameters for each subject using GPS coordinates. There were significant sex differences in activity range size and multiple movement parameters. Throughout the active season males had greater activity range sizes and showed greater movement than females. This trend was pronounced during the mating season, which was restricted to late summer and early fall (late July through September). In contrast to most populations of A. contortrix from more southern and western localities, we did not observe any sexual activity (e.g., courtship, coitus, and male-male fighting) in the spring. Individuals of both sexes showed annual fidelity to: (i) activity range location, (ii) activity range size, (iii) movement distances, (iv) particular features of their activity ranges (e.g., refuge sites), and (v) hibernation sites. Males and females showed no difference in preferred seasonal habitats. In both sexes, shifts in habitat associations during the active season included migrations from over-wintering sites within basalt trap rockslides to upper-elevation, open deciduous forest during the summer foraging and reproductive season. Parturition in the field was recorded in eight instances and was always close to one of the two hibernacula used by the individuals in the study area.
Proceedings. Biological sciences / The Royal Society, Jan 7, 2014
Contest decisions are influenced by the outcomes of recent fights (winner-loser effects). Steroid... more Contest decisions are influenced by the outcomes of recent fights (winner-loser effects). Steroid hormones and serotonin are closely associated with aggression and therefore probably also play important roles in mediating winner-loser effects. In mangrove rivulus fish, Kryptolebias marmoratus, individuals with higher testosterone (T), 11-ketotestosterone and cortisol levels are more capable of winning, but titres of these hormones do not directly mediate winner-loser effects. In this study, we investigated the effects of winning/losing experiences on brain expression levels of the receptor genes for androgen (AR), oestrogen α/β (ERα/β), glucocorticoid (GR) and serotonin (5-HT1AR). The effect of contest experience on AR gene expression depended on T levels: repeated losses decreased, whereas repeated wins increased AR gene expression in individuals with low T but not in individuals with medium or high T levels. These results lend strong support for AR being involved in mediating winn...
Southeastern Naturalist, 2011
Physiology & behavior, Jan 19, 2015
Reception of pheromone cues can elicit significant physiological (e.g. steroid hormone levels) ch... more Reception of pheromone cues can elicit significant physiological (e.g. steroid hormone levels) changes in the recipient. These pheromone-induced physiological changes have been well documented for male-female interactions, but scarcely in same-sex interactions (male-male and female-female). We sought to address this dearth in the current literature and examine whether mangrove rivulus fish (Kryptolebias marmoratus) could detect and, ultimately, mount a physiological response to the pheromone signature of a potential, same-sex competitor. We examined steroid hormone levels in mangrove rivulus exposed to one of three treatments: 1) isolation, 2) exposure to pheromones of a size-matched partner, and 3) pheromone exposure to a size-matched opponent followed by a physical encounter with the opponent. We found that exposure to a competitor's pheromone cues elicited a significant increase in testosterone levels. Increases in testosterone were similar across genetically distinct lineage...
Animal Behaviour, 2014
ABSTRACT Prior contest experiences can predictably alter an individual's contest performa... more ABSTRACT Prior contest experiences can predictably alter an individual's contest performance and probability of contest success. Although winner and loser effects have been well studied across many animal taxa, the mechanisms underlying these effects and their adaptive value currently are topics of intense interest. Two predominant hypotheses posit that contest experiences alter either an individual's perceived fighting ability or its actual fighting ability. We addressed these hypotheses, and potential physiological and behavioural mechanisms driving experience effects in the green anole lizard, Anolis carolinensis. Prior losers went on to lose a significant proportion of future contests while prior winners were equally likely to win or lose against size-matched opponents. Further analysis revealed that the loser effect arose as a result of individuals updating their perceived fighting ability following a loss. Both prior losing and winning experiences influenced future contest performance with prior losers decreasing and prior winners increasing their aggressiveness in subsequent contests. Status-dependent changes in metabolic physiology were not associated with the presence of the observed loser effect. However, contest status and contest performance interacted to influence metabolic physiology. Plasma glucose concentrations decreased as a function of the frequency of high-risk, escalated behaviours performed by eventual losers, and muscle lactate concentrations increased as a function of the frequency of low-risk threat displays performed by eventual winners. Our results support the notion that prior contest experiences influence an individual's perceived, not actual, fighting ability and that status-dependent changes in metabolic physiology are not a likely mechanism underlying the presence/magnitude of experience effects.
Herpetological Monographs, 2009
We studied the spatial and reproductive ecology of a population of Copperheads (Agkistrodon conto... more We studied the spatial and reproductive ecology of a population of Copperheads (Agkistrodon contortrix), a North American pitviper, in a basalt trap-rock ecosystem in the central Connecticut River Valley, a region that constitutes the northeastern extreme of this species' geographic range. Adult males (n 5 20) and females (n 5 15) were surgically implanted with radio-transmitters and tracked every 48 h during the active season (April through October) for three consecutive years (2001 to 2003). From late autumn to early spring (November through March), when snakes were hibernating and thus inactive, tracking was reduced to once per week. We generated data on movement and other spatial parameters for each subject using GPS coordinates. There were significant sex differences in activity range size and multiple movement parameters. Throughout the active season males had greater activity range sizes and showed greater movement than females. This trend was pronounced during the mating season, which was restricted to late summer and early fall (late July through September). In contrast to most populations of A. contortrix from more southern and western localities, we did not observe any sexual activity (e.g., courtship, coitus, and male-male fighting) in the spring. Individuals of both sexes showed annual fidelity to: (i) activity range location, (ii) activity range size, (iii) movement distances, (iv) particular features of their activity ranges (e.g., refuge sites), and (v) hibernation sites. Males and females showed no difference in preferred seasonal habitats. In both sexes, shifts in habitat associations during the active season included migrations from over-wintering sites within basalt trap rockslides to upper-elevation, open deciduous forest during the summer foraging and reproductive season. Parturition in the field was recorded in eight instances and was always close to one of the two hibernacula used by the individuals in the study area.
Proceedings. Biological sciences / The Royal Society, Jan 7, 2014
Contest decisions are influenced by the outcomes of recent fights (winner-loser effects). Steroid... more Contest decisions are influenced by the outcomes of recent fights (winner-loser effects). Steroid hormones and serotonin are closely associated with aggression and therefore probably also play important roles in mediating winner-loser effects. In mangrove rivulus fish, Kryptolebias marmoratus, individuals with higher testosterone (T), 11-ketotestosterone and cortisol levels are more capable of winning, but titres of these hormones do not directly mediate winner-loser effects. In this study, we investigated the effects of winning/losing experiences on brain expression levels of the receptor genes for androgen (AR), oestrogen α/β (ERα/β), glucocorticoid (GR) and serotonin (5-HT1AR). The effect of contest experience on AR gene expression depended on T levels: repeated losses decreased, whereas repeated wins increased AR gene expression in individuals with low T but not in individuals with medium or high T levels. These results lend strong support for AR being involved in mediating winn...
Southeastern Naturalist, 2011