Tame Parents Produce Tame Offspring, Which Matters

It is only a glimmer — the kind of glimmer one often gets when eyeballing new data. But the implications of this small discovery are enticing.

You see, I have been looking at our data on tameness, Since 2014, our team (mainly Kristin, Seth, Mina, and Nelson) has measured tameness of loons by creeping up to birds resting on the surface. We do this by first measuring our distance to the loon with a rangefinder and then paddling slowly in its direction, taking distance readings every few strokes. The final distance reading — just before the loon dives to avoid us — is our measure of tameness. Determined in this way, tameness varies from well above 50 meters to less than 2 meters. (In fact, some of our marked birds, like the male in Linda Grenzer’s photo above, find our approach so unremarkable that they simply veer slowly out of our path, instead of diving.)

We can examine the origins of tameness in far greater depth than most other studies, because we have tameness readings on many sets of close relatives in the study area. In fact, owing to the duration of our study, the limited natal dispersal of many individuals (especially males), and our efforts to find adults that we banded as chicks, we now have tameness measured for 60 sets of relatives. These include Linda’s male (“Clune”) and his son, who breeds on tiny Virgin Lake; the notoriously skittish male on Oneida-East and his full brother on Hughitt; and the Bear female and her full brothers on Cunard and Gilmore (all three banded 13-15 years ago on North Nokomis Lake).

As the figure below shows, we have noted a strongly and statistically significant relationship in tameness between parents and offspring. This pattern implies that either: 1) offspring inherit their tameness from parents, or 2) parents teach their offspring to be tame or skittish during the chick-rearing phase (or both). Either way, similarity in tameness between adults and their young means that despite being measured on different lakes, many years apart, and at very different ages, tameness is stable within individuals and is largely fixed early in life. A loon’s degree of tameness is, in effect, part of its personality.

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Parent/offspring similarity in tameness is more than a hollow novelty. Since tame parents produce tame young (either via genetics or rearing environment), those young should respond to the habitat in much the same way as their parents. I am in the process of writing a proposal to the National Science Foundation to study, among other topics, the possible impact of loon tameness on habitat selection. Specifically, I wish to test the hypothesis that tame loons might be suited to lakes with lots of human recreational activity (generally large lakes) and skittish loons to lakes with limited human activity (generally small ones). If this logical hypothesis holds up, then pity skittish individuals. Since human activity is increasing, and even many small lakes now see frequent human usage, skittish loons appear to have a small — and shrinking — set of lakes on which they can breed. Moreover, the reduced chick production of small lakes might also doom skittish loons to poor breeding success, so that fewer skittish individuals are produced each year.

The long-term consequences of parents passing skittishness to their young and fewer offspring produced by skittish loons are easy to guess. Tame loons will produce a large proportion of all offspring in the northern Wisconsin population, and tameness should increase in frequency in coming decades to the point where skittish loons are hard to find at all. This vast behavioral shift might go unnoticed by most observers, since there will still be loons on the lakes. But to an ecologist, it is exciting to think that we might be on the brink of learning the precise mechanism by which a population of an important animal can become tame.