Biology 441. Animal Behavior

Midterm II. 10 November 1994

125 points - 5 points for name on top of each page.

40 pts. 1. Define and provide an example of each of the following (4 pts. each):

(15 pts.) 2. Label the axes of the graphs below and graphically depict the sonograms of (a) the typical alarm calls and (b) mobbing calls of songbirds. Discuss why these are similar or different.

a. Alarm calls

b. Mobbing calls

See Alcock for graphs.

"Seet" alarm calls are used in response to flying predators in the distance. These calls are used to warn mates and offspring of potential danger. Seet calls are softer than mobbing calls and of higher frequency (7-8 kHz). Seet calls attenuate after traveling a much shorter distance than a mobbing call. Seet calls are outside of the normal range of hearing for hawks and falcons. The attenuation of seet calls compromises their effectiveness in reaching distant, legitimate receivers, but decreases the chance that it will alter the predator to the caller's presence. Seet calls are very similar across unrelated species.

Mobbing calls are used for perching or roosting predators. These calls are ouder than seet calls with most of their energy in the 4.5 kHz range (lower than seet calls). These are used to attract others to join in harassing predators.

(20 pts.) 3. Use the following graphs to answer the following questions. In (a) determine sequential patterns of settling for the first 10 individuals attempting to settle in a particular area where two habitats are available. Once those 10 individuals have settled what is the approximate expected fitness of residents of habitat A? ________. of habitat B?_________.

In (b) determine the sequential patterns of settling of the first 8 individuals attempting to settle in the area. Once those 8 individuals have settled, what is the approximate expected fitness of residents of habitat A?________of habitat B?___________.

(10 pts.) 4. Generally we assume that individuals in groups will compete with each other for resources and have lower rates of food intake than when solitary. Is this assumption likely valid for black-headed gulls? Why or why not?

Black-headed Gulls may be an exception to this generality. Alcock summarizes Frank Gotmark's studies showing that individual foraging success is highest in flocks of 6, intermediate in flocks of 3, and lowest for single gulls foraging on schooling fishes in a shallow pool in a large indoor aviary (see pp. 340-341). Flocks of gulls disrupt the school, making it easier for all gulls in the flock to single out and capture individual fish. (Also, black-headed gulls leaving the colony alone vocalize and recruit companaions on their way to foraging areas, supporting the hypothesis that gulls flock to increase their foraging success.)

(15 pts.) 5. Alcock summarizes studies showing that Thomson's gazelles stott when they detect hunting cheetahs. (a) Provide two possible reasons why gazelles stott in such situations and explain why they are likely correct or incorrect based on the information Alcock presents.

Alcock summarizes several hypotheses (to better view the habitat for other predators lying in wait, to warn conspecifics, to coordinate escape with others, to confuse the predator(s), to notify the predator that it has been seen). Gazelles stott when alone (not predicted by the second, third or fourth hypotheses)and in short-grass savannahs (in apparent contradiction to the first hypothesis). Cheetahs abandon hunts of stotting gazelles more often than hunts of gazelles that do not stott, in support of the last hypothesis. You should be somewhat wary of the logic of this approach, however: perhaps there is strong selection in favor of stotting in high grass to detect predators lying in wait, but little selection against stotting in low grass, so the behavior "carrries over" to short grass, for example.

(b) Cheetahs are "stalking" predators, relying on stealth, and usually have little chance of success if they are detected at a distance. African wild dogs also hunt Thomson's gazelles and are "coursing" predators. They may chase Thomson's gazelles for several kilometers before capturing one of the gazelles. Would you expect Thomson's gazelles to stott once they have detected African wild dogs? Why or why not?

If gazelles are signaling predators that they see the predators and stotting slows their escape (actually it doesn't seem to slow them down), stotting would not be expected in response to African wild dogs. If they are signaling their condition by stotting, however, high stotting rates (or exceptionally high stotts) could advertise unprofitability.

For your information, gazelles do stott in response to wild dogs and gazelles stotting at lower rates are killed more frequently than gazelles stotting at higher rates, supporting the "advertising unprofitability" hypothesis.

(10 pts.) 6. There are a number of studies showing that predators don't consume size classes of a particular prey species in proportion to their availability and don't necessarily take the biggest or most abundant size classes of prey. Discuss one well-documented example and explain why prey size selection differs from prey size availability in the example you have chosen.

You could choose an example like selection of 7 mm polychaete worms by redshanks when 8 mm is the most abundant size class (from lecture) or medium-sized mussels (rather than the largest or most abundant size classes) by oystercatchers (from Alcock). In both of these examples, the predator is selecting those size classes of prey that provide it the highest net caloric benefit, once the difficulty of prey capture and handling is considered.

(10 pts.) 7. Explain how honeybee workers that have found a distant food source (e.g., 100 meters from the hive) communicate information about distance and direction of the food source to other workers within the hive.

Information is provided to other workers by the waggle dance. The waggle dance is somewhat like a figure 8 with the middle portion of the 8 forming a straight line run. Within the hive, the orientation of the "run" relative to vertical, with the sun symbolically represented as being vertical, provides information about direction. Distance is conveyed primarily by the number of waggles/run and the overall activity level of the bee: higher activity levels denote shorter distances. Note: all workers are females.

Back to lecture notes index.

Back home.