Publication Date

2012-04-23

Availability

Open access

Embargo Period

2012-04-23

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PHD)

Department

Biology (Arts and Sciences)

Date of Defense

2012-03-23

First Committee Member

Richard R. Tokarz

Second Committee Member

William A. Searcy

Third Committee Member

Donald L. DeAngelis

Fourth Committee Member

Maureen A. Donnelly

Abstract

Parental care is essential to the success of both parents and offspring in many species, and plays an important role in the evolution of animal mating systems and life histories. The mechanisms that regulate the intensity and form of parental care in a species are determined by many factors and are highly variable across taxa. However, our understanding of the behavioral ecology of parental care is built on research that is highly taxonomically biased to birds, with some studies also in mammals, arthropods, and fish. Amphibians display an impressive diversity of form in parental care, yet few studies of parental care have explained the mechanisms behind parental behaviors in this vertebrate class. Accordingly, the research in this dissertation tested four hypotheses about parental care in a species of dendrobatid frog that displays complex parental behavior, the strawberry poison frog (Oophaga pumilio). In this species, father frogs guard egg clutches in the leaf litter for approximately one week. When eggs hatch into tadpoles, mother frogs return to transport tadpoles individually to small terrestrial water pools such as those in the axils of a bromeliad plant. For approximately six weeks, mother frogs continue to visit tadpoles. When mother frogs visit, tadpoles display a vibration behavior. Then, mother frogs supply unfertilized eggs to their tadpoles as their principal source of food. To develop a thorough understanding of the behavioral mechanisms at play between mother and offspring O. pumilio, this dissertation tests hypotheses related to offspring discrimination, the use of multimodal sensory cues, honest signaling, and provisioning of potential chemical defenses. Studies mostly made use of behavioral tests and observations in the laboratory and in the field at the La Selva Biological Station in the lowland wet forest of Costa Rica. To facilitate observation of the interactions between mothers and tadpoles in a natural setting as well as easy access to large quantities of tadpoles, an extensive setup of 1000 artificial tadpole-rearing sites (“cups”) was installed on the trees in abandoned plantations adjacent to primary forest. Mother frogs used cups to deposit and feed tadpoles just as they would the natural phytotelmata in their habitat. Furthermore, motion-activated IR video cameras were installed at the site to permit 24-hour observation of mother-offspring interactions. Findings demonstrated that mother frogs use indirect recognition to locate tadpoles, and rely on honest signals of hunger from tadpoles to allocate nutritive eggs. Tadpole begging signals are likely reliable because of a significant cost of signal production via reduction in growth and as a result of a differential benefit of maternal eggs. Tadpoles use visual and tactile cues to discriminate between mother frogs and other visitors such as other species of frogs and potential predators when deciding whether to signal their level of need or to avoid predation. The eggs that mother frogs provide tadpoles as nourishment may also be provisioned with alkaloids that could provide chemical defenses for offspring. Thus, the behavioral mechanisms described in this research explain how mother O. pumilio determine who, when, and how much to feed, as well as how both tadpoles and mothers contribute to reducing the risk of predation to offspring.

Keywords

chemical defense; honest signaling; mother-offspring communication; offspring discrimination; parental care; poison frog

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