Date of Degree

9-2016

Document Type

Dissertation

Degree Name

Ph.D.

Program

Psychology

Advisor

Mark E. Hauber

Committee Members

Thomas Preuss

Dan P. McCloskey

Janis Dickinson

Subject Categories

Behavior and Ethology | Ornithology | Other Animal Sciences | Other Ecology and Evolutionary Biology | Zoology

Keywords

Cooperative breeding, Phenotypic Plasticity, Brood Parasitism, Eusociality, Israel, Social behavior

Abstract

Exploration and explanation of the relationship between individual variation in behavior and the composition and adaptive success of social groups or populations are crucial problems in the fields of behavioral ecology, ethology, and comparative psychology. These questions have been the subject of a longstanding discussion at both the proximate and ultimate levels of inquiry. Adaptive mechanisms explaining social decision making, both in terms of affiliative and competitive partner choices, are at the center of such discussions. Inclusive fitness, kin-selection, handicap or prestige, risk seeking and risk avoiding strategies, pay-to-stay/reward principles, as well as other theories have been proposed and supported as these mechanisms in a variety of taxa; theories which may not be mutually exclusive. This dissertation focuses on the role of individual ontogeny in the organization of a series of charismatic social systems. Specifically, I review evolutionary aspects of siblicidal and brood parasitic systems, and present research on social/cognitive ontogeny and interactive behavior of a passerine avian cooperative breeder (Turdoides squamiceps), a phenotypically reversible teleost fish (Astatotilapia burtoni), and a eusocial mammal (Heterocephalus glaber). The theme adaptive behavioral response to fluctuating or uncertain environments and interactions unites these taxonomically diverse subjects.

In Chapter 1 I review a potential evolutionary trajectory from siblicidal behavior to both obligate and intraspecific brood parasitism. This analysis focuses on a series of fitness inequalities that may function as the most parsimonious explanation of such an evolutionary trajectory. When resources provided by parents are limited, full siblings may be driven to siblicide. The inherent fitness cost to parents of siblicidal behavior by offspring may be offset by brood parasitism. Brood parasitism, however, carries its own costs, both in conspecific/intraspecific brood parasitism (where individuals in a population may still be related, requiring a kin-selected balance for any fitness advantage to result) and in interspecific brood parasitism, where the host may not be equipped to nourish offspring as effectively as biological parents. Chapter 1 also discusses the ultimate mechanisms for the evolution of one ontogenetic style to the others. For intraspecific brood parasitism to evolve from siblicide, the alleles shared with the parasitic parents by the surviving, parasitically laid offspring must exceed those eliminated from the population via competition between the parasitically laid offspring and host offspring. For interspecific brood parasitism to evolve from siblicide or intraspecific brood parasitism, offspring lost to siblicide or related individuals lost to intraspecific brood parasitism must be less than those lost to nutritional or behavioral mismatches which result from heterospecific parental care by foreign host taxa.

Chapters 2 and 3 were developed in association with the Arabian Babbler Research Project, a 40+ year old ongoing study using a habituated and ID banded population of Arabian Babblers in Hazeva, Israel, maintained by Professor Amotz Zahavi. The habituation of these cooperatively breeding passerines to observer presence permits detailed long-term data sets and analysis of individual life histories. Arabian Babblers live in exclusive, male philopatric social groups with high reproductive skew, where rank is strongly positively correlated with age. In Chapter 2 I demonstrate the relationship between ontogenetic experience and developmental stage and neophilic behavior in young Arabian Babblers (Turdoides squamiceps). I used a series of novel/familiar stimulus presentations to identify the latency to and frequency of approach to stimuli by young individuals. Stimuli yielded multimodal comparisons, including stationary objects, moving objects, and sounds. Each had a familiar and a novel condition. I found that all birds approached novel stimuli more frequently than they did familiar stimuli, and that intrabrood rank positively predicted frequency of approach. Additionally, juveniles were more likely to approach novel stimuli, and did so earlier in the presentation trials, than fledglings. All young individuals were more likely to approach when adults were present.

In Chapter 3 I use a dataset collected from 2002-2004 by members of the Arabian Babbler Research Project which details the behaviors occurring before and during the formation of allopreening dyads. Chapter 3 analyzes the role of autopreening in the formation of allopreening dyads, and presents evidence that it is a displacement behavior. Autopreening may occur before the social approach that is necessary to form an allopreening dyad. When relationships were hierarchically more certain (represented by an older actor in the dyad, or the formation of the dyad without invitation by the recipient) approach by the recipient occurred without autopreening. When recipients did autopreen, they were significantly less likely to approach the actor to form the dyad.

In Chapter 4 I present data from observation of a phenotypically reversible cichlid fish Astatotilapia burtoni. Socially mediated morphological plasticity in this species is largely driven by male intrasexual competition, and it is physiologically necessary for a male to develop the territorial phenotype in order to reproduce. Traditionally, analysis of A. burtoni communities divides males between territorial (DOM) and non-territorial (SUB) individuals based on an index that subtracts the total losses of an individual in intrasexual conflict from the combined total wins and courtship behavior exhibited by that individual. There are dramatic morphological, physiological, and behavioral differences between these two categories, defined as having either positive (DOM) or negative (SUB) dominance index scores. Chapter 4 uses cluster analyses to propose a formalization of a third male phenotype, identified with individuals transitioning between prototypical DOMs and prototypical SUBs. Specifically, a novel behavior was identified; a potential risk-avoidance strategy in which individuals appear to ignore challenges, rather than engage or flee. Other unique behavioral traits of this male phenotype, such as frequency of certain pigment displays, were identified, and the individuals were shown to be those more likely to transition across the traditional DOM/SUB division point of a zero score on the dominance index than either prototypical DOMs or prototypical SUBs.

In Chapter 5 I present the results of a preliminary rescue-behavior experiment using a eusocial mammal, the Naked Mole-Rat Heterocephalus glaber. The study population was individually tracked using subcutaneous RFID tags. This method permits high temporal resolution on location of individuals. The rescue scenario involved the experimental trapping of individuals at the distal end of tubes connected to the central enclosure. Cork was used to create an artificial “cave-in” that served as an obstacle for colony members. A plastic barrier prevented the escape of trapped individuals. A second permutation of the experiment used a bifurcated tube to present experimentally trapped individuals and empty space, both blocked by cork, simultaneously. Colony members were significantly quicker to excavate trapped individuals than empty space. Effort expended (defined as time spent in rescue and latency to initiation of rescue) varied by both caste and individual, with queens expending less effort than workers, and individuals initiating rescue events also being the most frequent actors in excavation.

In Chapter 6 I discuss the connections among these findings, as well as their relevance to contemporary questions in research on behavioral ecology and comparative psychology. Together, these manuscripts provide a taxonomically varied perspective on a central issue in sociobiology and cognitive ethology: the illumination of the role of individual ontogenetic experience on the adaptive function of social groups. This dissertation does not attempt to represent an exhaustive investigation of this complex subject. Instead, it highlights promising avenues of investigation and demonstrates that social systems which may differ greatly in organization and evolutionary history remain strongly influenced and constructed by interindividual variation in ontogeny and experience, with particular regard to decision making.

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