Be loved or be eaten: do signals adapt to differences in species composition?

Background

Mating displays provide a crucial reproductive signaling function and mating signals such as songs or colorations are often well-adapted to their local environment. Signal adaptation typically involves optimal detection by intended receivers such as mates and rivals. However, whether and how signals adapt also depends on their attractiveness to unintended receivers such as predators and parasites. The density and composition of signal receivers can differ dramatically between habitats. Unfortunately, whether differences in species composition affect signal evolution remains largely unknown.

We study selection pressures acting on sexual signals in two different environments, the tropical rainforest of Panama, and the nearby urban jungle of Panama City. We research the mating calls of tungara frogs and the sexual and natural selection pressures that act on them. Males gather at night in puddles and call to attract females, but their calling activity also attracts a wide range of other animals. We focus on two different eavesdroppers: predatory bats and parasitic midges that are both known to use the sound of the frog to find their meal. The frogs inhabit a wide range of micro-habitats, including relative undisturbed forests, tree plantations, agricultural fields, parks, dirt roads and other sorts of urban areas. We are currently interested in population-level differences in their calls and in particular whether any differences in call structure or behaviour can be related to changes in species composition.

Approaches

This project involves fieldwork at night and can be physically challenging. Calling frogs can be recorded, their calls analyzed and broadcast at various different locations to determine selection pressures acting on them. Other aspects involve manipulating the local environment around known or artificial call sites to assess how this affects receiver responses. Animals can also be taken from the field to a mesocosm or lab setup if this is necessary for behavioural measurements or experimental control. A minimum of 3 months fieldwork is required and restricted to the rainy season (April – November).

Supervision and information

Dr. Wouter Halfwerk
Room: H142, W&N building
Email:  w.h.halfwerk@vu.nl
Phone: +31 (0)20 – 59 82737

Prof. Dr. Jacintha Ellers
Room: H141, W&N building
Email:   j.ellers@vu.nl
Phone: +31 (0)20 – 59 87076