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← Theoretical A

Q18 — Animal Road Barrier Effect (Traffic Behavior Types)

Theoretical A Real exam question — full text reproduced under IBO's CC BY-NC-SA 4.0 license
Mechanisms of Behavior

Roads are responsible for habitat fragmentation, impeding wildlife movement via the “Barrier effect,” which combines direct mortality from collisions with animal avoidance behaviour. Note that animal response to moving cars can resemble their reaction to natural danger stimuli. The research identified four types of animal behavioural responses (see Table 1) based on their perceived danger from traffic. Each animal species typically exhibits only one of these behavioral responses.

Behavior type Description
Speeders Their primary response to threats is to flee across the road.
Avoiders Avoid the road at much lower traffic volume and remain further from the road than other types.
Nonresponders Do not cease their movement at any level of traffic intensity.
Pausers Reduce their speed by freezing, which increases the time spent on the roadway.

Table 1. Types of animal behavioural responses to traffic. Traffic volume entails the number of vehicles passing a point on a road segment.

Four line graphs (Western barn owls, Armadillos, Mule deer, Indiana bats) each plotting total barrier effect (B, black solid), mortality (M, blue dashed), and avoidance (A, red dotted) against traffic volume. Owls show B and M overlapping with A near zero (nonresponders). Armadillos show M dominating at low traffic and A overtaking M at a crossover point Z. Mule deer show an early mortality bump followed by a steep late rise in both B and A. Indiana bats show A rising steeply at very low traffic while M stays low. Figure 1. The total barrier effect (B, black solid line) from mortality (M, blue dashed line) and avoidance (A, red dotted line) for the four response categories. X - traffic volume in arbitrary units. Y - magnitude of the barrier effect in term probability (from 0 to 1).

On your answer sheet, indicate “T” for true statements and “F” for false ones.

A. Nonresponding behaviour is more likely to exist in top predators of a food chain.
B. Relative steadiness in the mortality of mule deer after an initial increase during low traffic volume is due to the mule deer's road-avoiding behaviour.
C. Point Z indicates the moment when armadillos are more likely to start pausing at the road edge than the road surface
D. Indiana bat is probably a speeder.
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Question reproduced from IBO 2024, Theoretical Exam Part A, licensed under CC BY-NC-SA 4.0 — attributed to the International Biology Olympiad. Open the full exam PDF · Community solutions (unofficial)