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Backyard Birder

Tracking our wildlife

A walk Sunday in neighboring Casalis State Forest found coyote, deer and fox tracks, as well as the tracks of a large dog along our chicken-yard fence.

A lot of activity goes on in the night, largely unseen and unknown to us humans.

I got to wondering why so many animals are active at night, a time when it must be hard to find food given limited ability to see in the dark.

I know the obvious answers.

For one, dividing a resource or habitat helps avoid competition. Some hawks and owls hunt the same areas, the hawks by day and the owls by night. Red-tailed hawks and great horned owls hunt open fields, one by day and the other by night. Red-shouldered hawks and barred owls hunt forested areas with the same diurnal/nocturnal division.

Some animals are nocturnal because nighttime offers more protection against their main predators. Mouse species, as one example, are comparatively safe in their burrows during daylight hours. We hear the telltale metallic click of the have-a-heart mouse trap as dark descends and our household mice become active.

Those are the standard answers: minimizing resource competition and greater safety from predators. Greater safety is relative, however, as many predators high on the food chain prowl the nighttime world. The tracks they leave behind in the snow tell many stories.

To go beyond the usual answers, I called Meade Cadot at the Harris Center. I mention Meade often here as someone I turn to for a deeper understanding of the ways of the wild world.

I resisted swapping reactions to the Patriots’ most improbable win a few hours earlier that afternoon. Instead I asked what had become a burning question: Why so much activity at night when sighting prey must be so difficult?

Meade said it goes back to the dinosaurs. Dinosaurs? How cool is that? I said something along that line.

Back in the days of the dinosaurs — about 165 million years of days of the dinosaurs — many dinosaur species successfully exploited every available ecological niche by light of day. Dinosaurs were diurnal.

That left the nighttime world as a broad, overreaching and available niche.

The first mammals appeared well after the dinosaurs were established, and the first known mammal species by fossil record was a small, shrew-like animal.

Shrews are often assumed to be mice or voles for their resemblance both in size and tunneling habits.

While huge dinosaurs roamed and hunted the land by day, this small, early mammal — perhaps the very first mammal and common ancestor of all mammal species that followed — hunted by night.

It’s a habit that Meade said “seems to have stuck” for a lot of its mammal descendants.

The same behaviors and adaptations that helped early mammals coexist with dinosaurs helped them survive the mass extinction that befell dinosaurs.

The meteor impact some 65 million years ago created debris that blocked the sun’s rays long enough to deprive herbivorous dinosaurs of their plant-based diet. Their quick demise led in turn to the demise of carnivorous dinosaurs that ate their vegetarian cousins. Large predators require large prey.

Meanwhile, mammals of the day — small and modest in their food requirements, warm-blooded and fur-coated compared to the dinosaurs — survived the mass extinction that took the majority of other animal species.

Absent the threat and competition of dinosaurs, mammal species evolved and multiplied rapidly to fill the abandoned niches in as many shapes and sizes as the dinosaurs before them, and then some. Many maintained nocturnal ways, developing along the way certain adaptations that helped them navigate the nighttime world.

Often you can tell a nocturnal species by its large eyes, eyes with retinas structured to maximize light-gathering although at the expense of color perception and focus.

As for acuity of hearing, there’s the oft-cited example of owls that can hear the rustling of mice and voles from an impressive distance. A deer’s large ears are perpetually cupped to magnify sounds, and can be turned directionally to get a better fix on any sound

As an example of smell acuity, on my Sunday walk I saw where two coyotes crossed paths in the night at right angles to one another. It looks like the second one detected the scent of the first and left urine marking exactly where the two crossed. Given a coyote’s sense of smell, that last message communicated a lot about the messenger.

A conversation with Meade led me into the amazing world of dinosaurs and mass extinctions, and thoughts of life of Earth and time’s great passing.

And hamsters.

An Internet site about the care of hamsters said they are nocturnal, near blind, and use smell, hearing and their whiskers (touch) to make their way in the world. It said that hamster owners often are surprised when the exercise wheels start spinning in the night and disappointed when their cute little pet sleeps through the day. Hamster owners were warned never to put their pets on a table or shoulder as a hamster’s weak eyesight can’t discern much beyond a few inches. Falls are therefore a danger.

I’m guessing that just about when our mouse-trap doors click shut, a hamster starts up on its rotary treadmill. Both share ancestry and nocturnal habits going back 200 million years. How cool is that?

Backyard Birder by Francie Von Mertens appears every other week in the Monadnock Ledger-Transcript.

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