Leaf Sheep

Photo Credit: Christian Gloor from Wakatobi Dive Resort, Indonesia

Meet the leaf sheep – it is neither sheep nor leaf. It is a sea slug! And it is likely the most adorable slug you will ever see. But what makes this slug amazing is not its appearance. Leaf sheep are multi-cellular animals that live in the sea. They can also photosynthesize sunlight for food!

This unusual species has beady black eyes and the face of a sheep, albeit a small one – the slugs themselves are only 1 cm long. They also have rhinophores (new word!) on top of their heads that look like ears or horns. These rhinophores give leaf sheep their sense of smell and ability to find food. Their bodies are clad in what looks like leaves, called cerata (new word #2!). These cerata are similar to the leaves of succulent plants, like zebra succulents or aloe.

Okay, but on to the photosynthesizing – here’s how it works. Leaf sheep graze on algae as sheep-sheep would graze on grass. As they do, they take in the chloroplasts from the cells of the algae and store the chloroplasts in the cerata. The chloroplasts are what contain the chlorophyll and allow photosynthesis to take place. So not only do leaf sheep eat algae, they supplement their diet through photosynthesis. The process of taking the chloroplasts from the algae and storing it is called kleptoplasty (another new word!). And yes, the root of this word is “klepto,” from the Greek word for thief. In other words, leaf sheep steal the undigested chloroplasts from the algae. If humans were able to do this, we’d eat a salad, store the chloroplasts in our system, then sit in the sun to make more food. It gives a whole new meaning to the idea of being solar powered.

Frog and Toad – Where Are They Now?

Boreal Frog

Boreal Frog (Photo Credit – Bryant Olsen)

In the spring I always welcome the croaks, peeps, and chirps of frogs and toads. As fall progresses toward winter, the songs fade. But where do the frogs and toads go? They are, after all, cold-blooded. Alaskan wood frogs actually freeze. No heartbeat. No blood flow. No movement. Nothing. As temperatures drop, their body flush with glucose produced in the liver, protecting the cells. It’s like having your own special antifreeze in your blood. In the spring the frogs thaw and hop away as if nothing’s happened, even though up to seven months may have passed!

Aquatic frogs drop to the bottom of their pond or other body of water. They don’t burrow in the mud though, they just hang out there to pass winter. Terrestrial frogs are a different story. These guys must burrow deep enough to get below the frost line or find cavities or crevices to squeeze into. This might include compost piles, in a beaver dam, in a mammal burrow, or in a gap between rocks. These frogs have the natural antifreeze, too, to help with extreme cold.

No matter the strategy, frogs and toads enter a state of torpor, a state of decreased activity when the heart rate and metabolism slow, and the body temperature drops. Among mammals this is called hibernation. But for frogs and toads, and other cold-blooded animals, this state is called brumation. Unlike hibernating mammals, amphibians and reptiles do not consume great amounts of calories to prepare for the winter. Their metabolism drops so low during the torpor that they cannot digest anything during this time. Brumation is triggered by cooler temperatures and fewer hours of daylight. Even in winter, these animals will move about on warmer days.

Black Bears

A week or so ago we had cold weather and snow. The calendar turned to November. At that time I decided it was okay to stop bringing the bird feeder in every night. The bears were hibernating, right? Wrong.

As I worked at home one cool morning, I heard crunching as something passed by our kitchen windows. I figured the sound was from deer, regular visitors to our yard. But what I glimpsed was much stockier than any deer I’ve ever seen. Lower to the ground. And furrier. A big black bear! And lucky for me, it came right up to the window by my desk. And the bird feeder? The bear wasn’t interested.

Black bears do not hibernate because of the cold but because their natural food sources (berries, insects, nuts, etc.) are no longer available. While they are preparing to hibernate, one bear consumes about 20,000 calories per day (fun fact – bears can smell food five miles away!). Based on the size of my visitor, it was right on track.

When black bears do hibernate, their metabolism and heart rate slow to about 50% of their waking rate. This conserves energy. During this time of torpor, they do not drink or eat for about 200 days. They don’t even use the bathroom! Scientists debate whether bears are actually true hibernators because they will wake up if they are disturbed. In addition, pregnant females awaken to give birth, and then to nurse. Some bears will even wake up, wander around, and then return to their den.

I’ve watched for that bear every day since its visit, but I suspect now it’s settled in for a long winter’s nap.


Red-Breasted Nuthatch

From a distance it’s sometimes hard to tell the difference between a nuthatch and a chickadee. The nuthatch is the one climbing down the tree headfirst or upside down on a branch. They are able to do this because of their strong toes and the large claws on their backward-facing toes.

These nuthatches use their strong feet to find insects and their larvae and eggs in the summer, and then nuts and seeds in the winter. In addition, these birds will cache food in the crooks and crevices of trees to save for times when food is scarce. They earned their name, “nuthatch,” because sometimes seeds or nuts are hard to break into. To solve this problem, these birds wedge the seed or nut into the bark of a tree to hold it in place, then hack at it with their beaks. That action is called “hatching.”

When nesting, a pair of red-breasted nuthatches usually digs out a cavity in a dead tree; the lazy (or smart?) ones use an old woodpecker hole. Once the cavity is excavated, they build a nest cup using grasses, mosses, and even shredded bark. They’ve even been known to steal nesting materials from other birds. But the coolest thing about their nests is the finishing touches they put on once they’re done. Red-breasted nuthatches smear the entrance to their nest with globs of resin from coniferous trees (their preferred habitat). Sometimes they carry the resin in their beaks. Other times they will carry it on stick or piece of bark and use it like an applicator! The nuthatches do this to keep out other birds, small mammals, and insects. When they want to get inside, the nuthatches just dive right through the hole.