Sept. 14th; Sensory Exploitation & Statistics Lab

In this lesson we start to analyze animal communication. Communication can take place between the same species (conspecific) or different species (heterospecific). Communication systems will continue as long as signalers and receivers gain fitness benefits from the interaction. There ware a variety of modalities for communication including; visual, chemical, auditory, electrosensory, and mechenical sensory. A resulting modification of communication is sensory exploitation.

Sensory Exploitation

In sensory exploitation, one individual sends a signal that activates a preexisting sensory emchanism already present in the reciever. An example of this can be seen in male cichlid fish. The males (signaler) possess large orange spots on its anal fin. The female (receiver) has evolved to brood her eggs in her mouth. Since the large orange spots on the males anal fins look the same as her eggs she will get close to his anal fin to pick up what she perceives to be her eggs. At this moment the male cichlid will release sperm into the females mouth hoping to fertilize the eggs she has already picked up.

This trait does not reduce the fitness of the female. Infact, by the fetilization of her eggs her genes are able to be passed on. This can explain why nature has selected for this trait. It has a benefit to the male and the female cichlid.

Another ‘colorful’ example of this sensory exploitation is the Orchid mantis. The ornate colors of the mantis attracts insects to him. The insects link color to nectar-filled flowers, hence their attraction to the Orchid Mantis.

Harmless Threat Displays

The majority of species will put on a harmless threat display. This saves the individual energy and minimizes the risk of injury from fighting. The barking gecko is a darling example of this sensory communication behavior.

Statistics Lab

Nonparametric Statistics

Female Hyena Have a Psuedopenis

1. Explain the extra androgen hypothesis and evidence that support or refute it.

The extra androgen hypothesis states that the Psuedopenis is cause by developing females with high levels of testosterone. The clitorus and penis are made from the same embryonic tissue. The reason that it is either a penis or a clitorus depends on the androgens the tissue is exposed to. However, studies have shown that pregnant females giving a androgen receptor antagonist had little effect on the daughters Psuedopenis.  

2. Give some alternate explanations for how the Psuedopenis may not be adaptive.

When hyenas greet each other they inspect anogenital regions. Hyena females are more dominant than males. During a greeting of two females, if one female has a Psuedopenis she may not be perceived as dominant. Hyenas with a Psuedopenis also produce high androgen levels that increases her size and aggression. This makes her an alpha, and alphas cubs get more food. 

3. How could sensory exploitation play a role in the adaptive origin of the Psuedopenis?

Sensory exploitation plays a role in the adaptive origins because of the social greetings that hyenas already possess.

4. What is one possible adaptive value of this structure that doesn’t support sensory exploitation?

One possible adaptive value of this structure that doesn’t support sensory exploitation is the increase of testosterone that makes these females more aggressive. This behavior enables them to increase their fitness, but makes are seen as weaker. When greetings occur they are perceived as the weaker sex. 

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