Lecture 20. Communication and Animal Behaviour

Communication is the transfer of information from one animal to another.
This transfer affects the current or future behavior and the fitness of one or both individuals involved.
Communication involves a signaller and a receiver, both of whom may alternate roles.

Bradbury and Vehrencamp (2011) developed a cost-benefit framework to analyze communication.
The framework considers the costs and benefits for both the sender and receiver.

Spotted hyenas engage in a greeting ceremony where they inspect each other's anogenital region.
Both males and females inspect each other's erect penis or pseudopenis.
L. Harrison Matthews proposed that the pseudopenis in females is due to high levels of testosterone during development (extra androgen hypothesis).
Research on free-living hyenas only partly confirms the extra androgen hypothesis.
Pregnant females do have elevated levels of male hormones, but these levels are lower than those in males.
Testosterone levels were lower when reproductive organs were forming.
Even when androgen inhibitors are administered to pregnant spotted hyenas, female offspring still develop a pseudopenis.
The development of the pseudopenis has become uncoupled from androgens.
Selection maintains the pseudopenis trait independently from other androgen-linked traits.

The pseudopenis may have adaptive value, considering the costs and benefits:
- High mortality rates during female birth (50% offspring, 70% female).
- Dominance enhances breeding success, leading to more cub survival, earlier breeding for offspring, and higher dominance for daughters.
- Male cubs are better accepted in other groups.

The extra androgen-extra aggression hypothesis is not consistent with females being more aggressive than males, despite generally having lower androgen levels.
Testosterone levels in females are unlikely to explain the maintenance of the pseudopenis.
Other hormones, such as androsterone (A4), have been found to be associated with masculinization of hyena females.

Evolution acts as a tinkerer rather than an engineer.
1. Pre-existing traits in senders (ritualization).
2. Pre-existing biases in receivers (sensory exploitation).
Sensory drive: Signals change to adapt to their environment.

Heather Proctor's research on water mites at Griffith University:
- Males exploit female feeding behavior by mimicking the vibrations of copepod prey.
- Hungrier females respond more to males.
- In response to the male's trembling, the female adopts a net stance to grab prey. If she grabs the male, he deposits spermatophores.

If sensory preferences precede the evolution of a signal, then novel signals resembling the preferred signal should still produce responses.

David Haskell's research:
- Artificial nests were placed on the ground, and recordings of begging calls were played.
- Much more depredation occurred at nests where begging calls of tree-nesting black-throated blue warblers were played.
- Ovenbird nests were more predated when playback was on trees.
- Nest predation occurs nevertheless (see control experiments).

Petra Quillfeldt found that chicks of Wilson's storm petrels beg more when they are in poor condition and require more food.

A single cuckoo chick mimics the calling of a full brood of reed warblers to deceive the reed warbler parents.

A relatively quiet blackbird chick was placed in a reed warbler nest, and a speaker played begging calls.
The reed warbler parents increased their feeding in response equally to the recorded cuckoo calls or the recorded reed warbler calls.
A speaker was used to isolate the effect of the begging call. Also a blackbird was used so it's begging calls do not resemble that of a reed warbler.

Female Túngara frogs prefer complex calls from males, but these calls make it easier for fringed-lipped bats to locate them (Mike Ryan).

The pitch of a rival's call affected the probability that a male European toad would pursue an attack.
Pairs were mating for 30 minutes, and playback of high and low pitched sounds was played when single males touched the mating pair.

Small toads cannot make deep croaks.
Begging birds attract the attention of predators.
Both parties may gain from honest signaling, and there will be selection to detect dishonest signaling.
Natural selection may lead to expensive signaling that guarantees honesty.
There may be a need for more than one signal working together to make it harder to 'cheat'.

Communication systems involve a signaller and a receiver—and sometimes an eavesdropper or illegitimate receiver.
Communication may be investigated at both proximate and ultimate levels of analysis.
Understanding the evolution of a communication system will require more than a knowledge of its current utility.
Within species, there is selection for honest signals.