Communication Between Animals

“Peacock tail display” by Vibin JK (CC by 2.0)

As you must know, animals cannot speak English, French, or Chinese. So how is it that animals communicate? Signals indicate intent and animals rely on a variety of visual, auditory, and mecanosensory signals to understand their other animals and make decisions.

Important Terms

  • Conspecifics:  members of the same species
  • Heterospecifics: members of different species
  • Types of Signal Modalities: ways in which animals communicate information to one another.
    • visual displays to signal information to another. For example, the fiddler crab mating dance. Success in finding a mate relies on the physical movements the crab makes, the size of the claw, and its coloration.
    • auditory signals are heard by the receiver and sometimes nearby eavesdroppers who can hear the signal as well.
    • chemical signals that are  left behind by the sender. For example, the odor that is left behind from a cat rubbing against tree so that other animals will smell and become aware of that cat’s presence.
    • electrochemical chemical secretions or emission of electric pulses sends information to nearby conspecifics /heterospecifics.
    • mechanosensory modalities are physical contact such as touching and grooming. This is seen in chimpanzee groups who groom each other.
    • Animals can often undergo multiple modalities at once.
      • ie. a bird dances and sings to attract a mate- which uses a visual and auditory modalities to signal to the female that he is a good mate choice.
  • Sender/Receiver: The sender is the organism that creates the signal wile the receiver is the organism that is experiencing and gaining knowledge from the signal.  The signal must benefit both the sender and receiver for the signal to be adaptive. The receiver may change behavior after experiencing signal from sender.
    • Use of signal is a positive evolutionary trait- the allele combination and the phenotypic expression increase the individual’s fitness.
  • Eavesdropper: An individual is picking up on a signal that was not intended for it. This can be seen in predatory species who hear a finch’s social call and is able to locate and eat that finch.  Exploitation of the signal can be maladaptive for the sender.


“Meercats” by Nigel Swales (CC BY-SA 2.0) 

  • Meercat sentry behavior is a protective behavior, if a predator is seen then the sentry will call out so that everyone within range of hearing the call can hide.

Reasons for Communication:

  • sexual advertisement and mate attraction-  Antlers on a deer, bird dancing
  • parental care -begging of babies so that they are fed, recognition-know which offspring is yours
  • Environmental information-predator alarms, food location
  • Territory defense and conflict resolution
  • Social integration-contact calls to signal over others, especially in family groups, dialects can develop within various groups of the same species
  • Predator Defense-warning coloration

“Strawberry Poison Dart Frog (Oophaga pumilio)” by Caspar S (CC by 2.0)


Sensory exploitation:

  • Communication signals originate in actions that activate pre-existing sensory abilities of receivers.
  • The male water mite triggers predatory response of female to mate with her. Hungry females will mate more.
  • African Cichlid Fish: male has bright orange spots on anal fin, female may try to pick up what appear to be eggs on the fin. External sperm production fertilizes the female when she tries to get the dots on his tail. Mutually beneficial—adds to probability that this will continue to evolve over time.
    • Possible Experiment: add orange dots to a male of a closely related species to see if it will cause the females to exhibit the same behavior as the female cichlid fish. ***retention of an ancestral trait****
  • Coloration on spiders attract insects and prey. Only the signaler benefits from this sensory communication. Coloration is a fitness benefit for the spider.


  • Selection only acts on pre-existing traits that developed for a past environmental situation.
    • Panda Principle: The panda has five fingers but no thumb so over time the wrist bone has come to function as a thumb. Ancestral pandas walked on all fours, but as they started walking upright and needed to grab bamboo the wrist bone developed into a thumb-like structure.
    • Moths can detect ultrasonic sounds of bats (predator defense) ~and over time in some species like the whistling moth males can produce ultrasonic sounds that will attract females ~“tapped into evolutionary potential”
  • Behaviors that animals exhibit are part of its evolutionary history.

Conflict Resolution:

Why waste time, energy or risk death?

  • Mantis does a harmless threat display instead of fighting.
  • Barking Gecko: small ones have high pitches bark; large ones have low pitch bark. Predators ans other geckos can distinguish the two and decide whether or not to fight.
  • Another example- antler flies and deer bucks use size to determine dominance, however, they do not fight to the death

“Deer-Newport News Virginia” by C Watts (CC by 2.0)

Honest signaling

  • Communication and signal modalities accurately depict the organism’s size and abilities to others.
  • Live to fight another day
  • For example, Collard lizards have UV reflective patch on their mouths. The bigger patches correspond to larger mouth so smaller subordinates back off and do not risk death.

Dishonest signaling

  • Is selected against because it creates conflict and has a great fitness cost.
  • More black color on face of paper wasps indicates that it is more aggressive. Wrestling occurs between conspecifics to test this assumption. The stronger wasps with the black survived throughout evolutionary history, passing the aggression and black color onto the next generation. This is an example of selection favors honest signaling. If the black faced wasps were weaker then they would have died off during the wresting displays and the yellow faced wasps would be the more aggressive type.

Signal Deception

  • male Photinus flies flash to attract female of their species but sometimes a female Photuris responds instead and she eats him instead of mating. Different species of fireflies have evolved different flash patterns-speciation
  • Illegitimate signaler: an individual makes a signal to fool members of another species.
  • Signal deception in plants for exmple- The Elbow Orchid has flowers with lip that looks like a female wasp. The males are attracted to the plant and thus the pollen is spread.
  • Carnivorous plants-looks like a flower for bugs to get pollen and nectar from but uses a visual display to deceive prey.

Maladaptive Behavior

Why do animals sometimes do the wrong thing? Get fooled by a signal and die?

  • doing something that decreases an animal’s fitness
  • Novel Environment Theory: An animals adaptations are based upon previous environments in which its ancestors lived. New environments, constraints, or human interference to create alternative environmental situations cause an animal’s adaptations to decrease in their fitness benefits. For example, the introduction of plastic bags to sea turtle environments, plastic bags look like jelly fish which they evolved to eat but eating a plastic bag kills the turtle.
  • Female hyenas have a pseudopenis. Sensory exploitation? Maladaptive-makes it hard to mate, need to be aggressive to get food? Greeting ceremony benefit?
  • Net Benefit Theory: if you never respond you will never mate. Cost vs benefit where the potential benefit greatly outweighs the potential cost to fitness.
  • Adaptations (benefits > costs of traits) are not always perfect. Just must contribute more to fitness on average compared to other alternative traits for survival and reproduction of the genes associated with that behavior/adaptation.


  • intercepting/hearing/seeing a signal to use for one’s own benefit.
  • Bats can hear a frog’s mating calls and locate it so that it can eat it.
  • A finch could be social calling to others and a predator swoops in and eats it.
    • adapt to use a frequency/volume that the predator cannot hear
      • “seet call” so hawk cannot hear
      • “mob call” calls in conspecifics to attack hawk.
      • Via predation pressure in an evolutionary ancestor due to eavesdropping of the predator.


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