Chapter 52, Problem 14TYU

INTERPRET DATA Look at the two graphs in Figure 52-21. In which experiment did the parentals in the experimental group guard the eggs more closely? In which experiment did the experimental parentals guard the young more closely? Account for these differences.

RESULTS:

Experiment 1: As indicated on the y-axis, which measures level of parental care, parentals reduced their level of guarding the eggs. Eight of the males in the experimental group abandoned their nests, and egg defense was significantly lower in this group compared with that in the control group. However, after eggs hatched, there was little difference in parental care of the young between the two groups.

Experiment 2: During the egg phase, there was little difference in level of parental care between experimental and control groups. However, after eggs hatched, the experimental parentals significantly decreased their level of guarding the nest.

CONCLUSION: Male bluegill sunfish adjust their level of parental care according to their level of perceived paternity.

In Experiment 1, parentals provided less care when they perceived that the eggs may have been fertilized by sneaker males. After the eggs hatched, olfactory cues indicated that the offspring were indeed their own, and their level of care increased.

In Experiment 2, parentals cared for the eggs even though some had been swapped. However, after they hatched, olfactory cues from the offspring indicated that they were not the parental’s own offspring. The level of parental care decreased significantly.

SOURCE: B.D. Neff, Nature, Vol. 422 (April 17, 2003): 716–719.

Figure 52-21 Decisions about parental care