Biology 484 – Ethology

Chapter 6 – Behavioral Adaptations for Survival

Chapter 6 Opener Canyon treefrogs rely on camouflage to protect themselves from predators

Camouflage is a classic way of being protected from predation.

Figure 6.1 Mobbing behavior of colonial, ground-nesting gulls

Mobbing behavior offers protection to young in nesting sites by the adult silver gulls.

Figure 6.2 A nesting colony of black-headed gulls

The behavior of colonial living affords many benefits (and challenges) for individuals. Increased changes of survival against predators is a major benefit.

Figure 6.3 An arms race with a winner?

The competitive struggle for survival is seen here. The salamander being consumed actually produces a very highly toxic poison which protects it from many predators. In this case, the garter snake is not affected by the toxin, and therefore the salamander’s defense has been thwarted.

Figure 6.4 Does mobbing protect eggs?

The title of this slide poses the question…. How would you answer it from the graphical information provided?

Figure 6.5 Benefit of high nest density for the arctic skua

Note the difference between high density populations and low in terms of survival of larger numbers of young.

Figure 6.7 Not all gulls nest on the ground

Most gulls are ground nesters, but the Kittiwake Gull is a cliff nesting species.

What would you predict may have lead to this behavioral shift?

Figure 6.8 The logic of the comparative method

Figure 6.9 Colonial California ground squirrels mob their snake enemies

Mob behavior in a mammalian species is less common, but shown here in the California Ground Squirrel.

Figure 6.10 The dilution effect in butterfly groups

As population size increases in this butterfly species, the risk of predation for any single butterfly decreases markedly.

However, what other factors may alter this effect?

Figure 6.12 The dilution effect in mayflies

Convergent hatching dates, can offer the dilution effect in many species.

The next three slides show examples of behavioral groupings that will result in increased survival.

For each, can you identify how protection is occurring?

Figure 6.13 Fighting back by terns and wasps

Figure 6.14 Communal defense by sawfly larvae

Figure 6.15 A group of sleeping bees

Figure 6.16 Cryptic coloration depends on background selection

Crypsis is to have features or colorations that allow an organism to be masked or hidden in its environment. Here we see that the background selection is CRUCIAL in this protection. Think back to the “Thinking Like A Predator” lab experience for further comparison.

Figure 6.17 The camouflaged moth, Biston betularia

This is the same classic species studied to suggest population change as a driving force in evolution.

Figure 6.18 Predation risk and background selection by moths

Figure 6.19 Cryptic coloration and body orientation

Interestingly, sometimes the crypsis is quite specific and as in this case, is highly dependent upon position behaviors held by the moth in this image. If the moth were to adopt a different position (which it typically does not) when alighting on the bark, it would less cryptic.

Figure 6.21 Safety lies in false edges

Lines can be used to blur or highlight position of animals.

In B, the prominent dark/light patches blur the full position of the grasshopper, even suggesting a head region that a predator may anticipate to follow in a particular direction.

In C, the bold patches are across the entire grasshopper (which is toxic) to help announce its presence to a predator for protection.

Figure 6.22 Personal hygiene by a skipper butterfly larva may be an antipredator adaptation

The cleaning behavior this species engages in has been associated with lowered rates of predation.

Glass beads serve as a non-odor bearing control equivalent to the leaf shelter containing many waste pellets.

In the experiment, there was no larva present, only the odor cue of the waste.

The wasp predator clearly visited and spent more time at the sites with waste than those without waste.

Figure 6.23 Warning coloration and toxins

Each distinctly colored species shown has a toxin that it is “announcing” it has via its distinct coloration.

Figure 6.24 Effect of monarch butterfly toxins

Figure 6.26 An advertisement of unprofitability to deter pursuit?

Stotting behavior in the antelope is designed to conspicuously show predators that “I am fit and healthy and energetic…. I will be able to outrun you…. So do not bother pursuing me!”

Figure 6.27 Cheetahs abandon hunts more often when gazelles stot

Figure 6.32 Selfish herds may evolve in prey species

A revolutionary work from the mid 1970s that reshaped our ideas about how to examine selection pressures in a species.

The key idea is that most every response an animal makes in its interaction with its environment (and hence others in its environment) can be described in a way that suggests “selfish” self-preservation of the genes of the animal.

This was rather controversial in the 70s but is widely accepted as logical today.

Figure 6.33 Redshanks form selfish herds

Birds of this species that end up being preyed upon are on average FARTHER away from neighbors than non-targeted birds, suggesting a “selfish” behavior.