Extrinsic stressors modulate resource evaluations: insights from territoriality under artificial noise

Abstract

Background Competition is considered to rely on the value attributed to resources by animals, but the influence of extrinsic stressors on this value remains unexplored. Although natural or anthropogenic environmental stress often drives decreased competition, assumptions that this relies on resource devaluation are without formal evidence. According to theory, physiological or perceptual effects may influence contest behaviour directly, but motivational changes due to resource value are expected to manifest as behavioural adjustments only in interaction with attainment costs and resource benefits. Thus, we hypothesise that stressor-induced resource devaluations will impose greater effects when attainment costs are high, but not when resource benefits are higher. Noise may elicit such effects because it impacts the acoustic environment and imposes physiological and behavioural costs to animals. Therefore, we manipulated the acoustic environment using playbacks of artificial noise to test our hypotheses in the territorial male Siamese fighting fish, Betta splendens. Results Compared to a no-playback control, noise reduced defense motivation only when territory owners faced comparatively bigger opponents that impose greater injury costs, but not when territories also contained bubble nests that offer reproductive benefits. In turn, nest-size decreases were noted only after contests under noise treatment, but temporal nest-size changes relied on cross-contest variation in noise and comparative opponent size. Thus, the combined effects of noise are conditional on added attainment costs and offset by exceeding resource benefits. Conclusion Our findings provide support for the hypothesised modulation of resource value under extrinsic stress and suggest implications for competition under increasing anthropogenic activity.

Complex strategies: an integrative analysis of contests in Siamese fighting fish

“…Here we address this by using an integrative sequential analysis of behaviour during territorial contests in male Siamese fighting fish, Betta splendens. These contests play a significant role in reproductive success due to the use of territories to build bubble-nests for their offspring, which contributes fundamentally to the survival and development of eggs and prepares males for mating [23,24]. Thus, a territory has great fitness value that can drive highly aggressive behaviour both by males looking to build nests and those protecting existing ones [23][24][25][26][27].…”

“…These contests play a significant role in reproductive success due to the use of territories to build bubble-nests for their offspring, which contributes fundamentally to the survival and development of eggs and prepares males for mating [23,24]. Thus, a territory has great fitness value that can drive highly aggressive behaviour both by males looking to build nests and those protecting existing ones [23][24][25][26][27]. This aggressiveness underlies the lengthy, physically taxing and often deadly interactions necessary to resolve contests.…”

“…Such strategic decisions by B. splendens, whether for wining or minimizing costs, involve a welldocumented, stereotyped and easily identifiable behavioural repertoire [29,30]. This includes frontal displays with extended gill-covers and lateral displays with spread fins for signalling size, biting and tail-beating attacks for inflicting physical injury, and retreats for avoiding attack or signalling submission [23][24][25][26][27][28][29][30][31]. Even though evidence is rare, these behaviours have been noted to exhibit chronological organisation during contests and individual variation due to underlying personality-trait aggressiveness [31,32].…”

“…Even though evidence is rare, these behaviours have been noted to exhibit chronological organisation during contests and individual variation due to underlying personality-trait aggressiveness [31,32]. In addition, the behaviours can be adjusted to assessments of RHP and the perceived value of defended territory, which can vary in quality with noise disturbances and 'subjectively' with the construction of bubble-nests [23][24][25]. Finally, recovery from mid-contest startles has been repeatedly validated as an independent measure of fight motivation across species, including in B. splendens where it exhibits similar but different strategic modulation to behaviour [20,24,25,33].…”

Quality of Death in Fighting Bulls during Bullfights: Neurobiology and Physiological Responses

“…During bullfights, the physiometabolic responses correspond mainly to the presence of different types of stressors, such as physical (tissue injury, pathologies, pain [3]), environmental (extreme weather, microclimate, nutrition, handling [4], transportation [5], noise [6]), and psychosocial factors (social isolation, overcrowding, pain, fear or distress [7]). For fighting bulls, similar to any other mammal, the response degree and the consequence in their homeostasis depends on the stressor type, the duration of the stimulus, and the previous experiences of the animal [8,9].…”