Self-study
A recent study examined the daytime and nighttime activity patterns of two populations of tree-dwelling lemurs—the first living in a rain forest, where tree canopy cover is consistent year-round, and the second living in a deciduous forest, where many trees lose their leaves during the winter months. ████ ██████ ██ ██████ ████ █████ ██ ██ ████ █████████ ██████ ██████ ██████ ████ ████ ████ ███ ████ ██ ███ █████ ████████ ███ ██████ ████████ ██ █████████ ████████ ███ █████████████ ████ ██████████ ███ ███ ██████████ ██████ ██ ███ █████████ ██████ ████ ██ ███ ███ ███ ██████████ ██████ ██ ███ ████ ███████
"Surprising" Phenomenon
Why does winter nocturnal activity increase much more for tree-dwelling lemurs in a deciduous forest, where trees lose leaves in winter, compared to those in a rainforest, where tree canopy cover stays the same all year?
Objective
The correct answer will propose a hypothesis explaining a key factor that causes lemurs in a deciduous forest to have more winter nocturnal activity than those in a rainforest. This factor must depend in some way on the tree canopy cover in the forest and will thus affect the lemurs’ behavior differently depending on their environment.
19.
Which one of the following, ██ █████ ████ █████ ██ ███████ ███ ██████████ ███████ ███ ███ █████ ███████████ ████ ███████ ██ ██████ ████████ █████████
a
For both lemur ████████████ ███ ███████ ███████████ ███ ████ █████████ ███ ███████ ██████ ██████ █████████
The fact that both lemur populations’ competitors are active during daylight has nothing to do with tree canopy cover and does not explain why lemurs in the deciduous forest had much more nocturnal activity than those in the rainforest.
b
The primary predators ███ ████ █████ ███████████ ███ ███████████ █████ ████ ████ ██ █████ ████████ ██ ████ ████ ██████ █████████
Lemurs in deciduous forests face greater predation risk in winter because the birds can see clearly without leaves. In rainforests, year-round leaves block these predators' view. Thus, to avoid predators, lemurs in deciduous forests are more active at night during the winter.
c
In both habitats, ███████ ██ █████████ ██████ ██████ ██████ ████████ ███ ████ ██████ ██████ ██████ ███████
This might explain why both populations are more nocturnal during the winter. However, because the snakes’ hunting isn’t affected by tree canopy cover, it doesn’t explain why lemurs in deciduous forests have more nocturnal activity than those in rainforests during the winter.
d
The lemur population ██ ███ ████ ██████ ██ █████ ███ ████ ██ ███ ██████████ ██ ███ █████████ ███████
Population size doesn’t explain why the lemur population in the deciduous forest has more nocturnal activity in the winter than the lemur population in the rainforest. We need a factor that affects the lemurs differently based on the tree canopy cover of their environments.
e
The lemur population ██ ███ ████ ██████ ████ ████ ██████ ███ ███████ ███████ ███ ██████████ ██ ███ █████████ ██████ ████ ████ ███████
Why would eating only plants cause the lemurs in the deciduous forest to have more nocturnal activity in the winter? We still need a factor that affects the lemurs’ winter behavior differently based on the tree canopy cover of their environments.