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Pikes/Pines | How the Hill’s creatures beat the heat

So, it’s summer, and it feels even warmer than last year and it’s barely rained. Most of us don’t have air conditioning at homes, but we can still go places that do to beat the heat, and (for now) it’s easy enough to turn on the water. Wild species don’t have those options. How do they combat high temperatures and lack of water in the summer?

Puget Sound’s climate is technically Mediterranean, with warm and dry in the summers that are exacerbated by the city’s cement and our control and capture of water for human use. Summer heat can be a serious challenge for plants and animals a like, and adaptive behaviors and physical traits help them avoid overheating or loosing vital moisture. Below are a few examples we can see on the Hill.

The Mid-Day Siesta
Many animals have figured out that being active during the height of the day ends with overheating and dehydration. We hear birdsong in the morning and evening because it’s less costly to be active then. Coyotes don’t simply retreat into the night as crafty little brigands, avoiding detection, but also because it’s far simpler to hunt using other senses and beat the heat. An extreme example of lowering activity levels in the face of higher temperature and drought is called estivation. Essentially a version of hibernation that addresses moisture levels by lowering vitals to a bare minimum, many invertebrates, like earthworms, slugs, and snails find a quiet places to wait out the drought and estevate.

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Snails hide in their shells to estivate. Credit: Brendan McGarry

Get Rid of Heat (Or How You Store It)
Humans are one of few species that can sweat to reduce our temperature and there are no other native species in the Pacific Northwest that can do so. Some animals can afford to escape to shade, but others don’t have that luxury as they need to be active all day to find food. You may have seen a crow or a pigeon during a hot day with its beak open. What you can’t see is that it’s vibrating its throat muscles in a form of ventilation called gular fluttering. By exposing moist membranes it allows for more evaporation, which helps regulate temperature. Dogs pant (and so do Coyotes), which allows hot air to escape the body rapidly while inviting cold air in. Mammals with fur also shed a winter coat, is an effective and flexible, albeit energy expensive way to manage temperatures. Another method is to have a large surface area to volume, which helps elongated flattened animals like cold-blooded garter snakes heat up and cool down quickly (which also allows them to need less energy than warmblooded animals because they use only external energy to warm or cool down).

Move (Or Stay Put)
If there’s no water around, mobile species leave to find it. In Summer you’ll find that a habitat with a water-source will have far more animal activity than one without. We don’t see Capitol Hill species migrating long distances because of lack of water (as some desert species might), but many of our songbirds do move to higher elevations after breeding for plentiful food and water in a places where slowly melting snowpack provides an extended season. On the flip-side, if you find a place to live that doesn’t change in temperature much, like say ants nesting underground or rats in our basements, you have less to worry about. Subterranean dwellings tend to stay a more ambient temperature year-round.

Hold Onto Your Water

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The fresh layer of bark that is full of chlorophyll in the Pacific Madrone. Credit Brendan McGarry

Keeping from overheating is a good way to diminish water loss, but what if you can’t move to a new spot? My favorite Capitol Hill example of dealing with drought is seen in the Pacific Madrone (Arbutus menziesii). This broad-leafed evergreen has found a niche in soils too well drained for more fast growing conifers, but this puts it at risk when there’s little or no rain. Having broad leaves year-round can create issues of water loss because more water-rich chlorophyl is exposed to the sun (and freezing temperatures too). However, it also means that the tree can take advantage of a long growing season and waxy leaves (think sunblock) help fend off regular assaults to moisture. The Madrone has also countered extremes with chlorophyl in its bark, an adaptation seen in many plants that live in arid environments. This allows them to drop leaves to decrease water loss. We don’t typically see healthy Madrones completely devoid of leaves but it aids them in leaf replacement and pulls them through dry times.

The reality of environmental extremes for most organisms is that some individuals don’t make it. This is ultimately what gives way to adaptations, as individuals with helpful genetic mutations survive to reproduce. It’s knowing things like that which make me excited about seeing plants and animals making it work in hard situations, like unusually hot or dry weather (or the urban landscape). In many ways our moderate climate makes it all the more difficult for species to deal with the occasional extremes. So, when you see a crow painting in the heat or notice a coyote scampering through the night realize they’re relying on adaptive traits to get them through the day, the same way our big brains have allowed us to create Air Conditioning or store water under Cal Anderson Park.

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Kivrin
Kivrin
8 years ago

This was a fun read—thanks!

Jessie BC
Jessie BC
8 years ago

This was a wonderful read!! Pikes/Pines continues to be my absolute favorite regular column on CHS. Keep it up!