Cave Life

This week is Cave Week, so to celebrate we're going spelunking to see what critters we can find. In addition to all sorts of whimsical formations, caves host a surprising amount of life. There are trogolobites, which live full time in caves; trogolophiles, which live in a cave but can also survive outside; and trogoloxenes, the part time cave denizens. You can encounter insects, fish, birds, mammals, plants, fungi, and others. Because there is very little natural light, many of these species are adapted to live in darkness; some don't even have eyes.

Whimsical cave formations

The first cave critter that comes to mind is a bat. Many bats roost in caves because they are cool and dark during the day, making it easier to sleep. Caves make a great place to hibernate over the winter. A constant temperature that is above freezing is an obvious plus, but it's cool enough to trigger the hibernation process. Other cave mammals include bears and jumping mice.

To the bat cave! (National Science Foundation)

Plants are a rare find in  caves because they need sunlight for photosynthesis. I saw ferns growing in a cave under a ceiling hole that opened to the surface. Much more common are fungi, which thrive in dark, damp conditions. Most important among them is Pseudogymnoascus destructans, which causes White Nose Syndrome in bats. It is devastating bat colonies across the US and Canada, and enjoys the cool temperatures while the bats hibernate.

White Nose Syndrome affecting these bats (NPS)

Cave fish are interesting little critters. Nearly all lack eyes and skin pigment. With no light to see by, there is no need to camouflage or stand out, so they are likely to be white or light colored. Unable to see their food, they find it by sensing movement in the water. What exactly do they eat? Since plants, the base of the food chain can't really live in a cave, anything in there either needs to go outside for good or eat whatever gets brought in. Cave fish eat detritus that washes in during rain events. Other critters get by on dung, the leaving of larger animals that way out.

Blind cave fish (NPS, Rick Olsen)

Cave Week runs through this weekend. Find a cave near you and check it out. Spelunk safely. Use the buddy system, carry at least three light sources, and make sure someone knows where you are going. Don't disturb any wildlife and make sure clothing and equipment are thoroughly cleaned before entering another cave. This helps prevent the spread of White Nose Syndrome.
This week's information comes from the National Park Service and National Geographic.

Wisdom of the Ages

While it’s cold and snowy where you are, it’s a warm sunny day on the Pacific atoll of Midway Island, where mating season just ended for the Laysan albatross. Most famous of these large seabirds is Wisdom, the oldest known wild bird. She’s at least 67 years old and still laying eggs. Being that old and still raising young makes me wonder just how long these birds can last.

Wisdom’s age was discovered in 2002 when her band was replaced. The biologist who replaced her band looked up her number and noticed that he originally banded her in 1956, and at that time she was an adult of at least 5 years old.

Wisdom (right) and her mate during nesting season (USFWS)

What is remarkable about this particular bird so special, at least to me, is that she managed to survive so many threats in her time, beyond the normal dangers like predators, disease, and typhoons. Working in her favor are the Migratory Bird Treaty and the US Wildlife Refuge System, protecting her and her kind from human predation and habitat loss at their nesting sites on Midway.

Working against Wisdom and other albatrosses are a whole host of man-made problems. Foremost among them is ocean plastic. Laysan albatrosses feed at night, and their food is fish, squid, and fish eggs that come near the surface. Sadly, floating garbage is also at the surface. In a tragic sequence of events common to marine life everywhere, they mistake plastic for food and either eat it themselves or feed it to their chicks. Despite having full stomachs, the birds and other critters die of starvation because plastic is not very nutritious.

Invasive species are also beginning to take a toll on the albatrosses. They have already been extirpated from the Hawaiian Islands, outcompeted or outright killed by the dogs, cats, pigs, and rats that accompanied Europeans as they traversed the Pacific. Now, the Midway colony is under attack by mice. While the birds are much larger than the mice, they succumb to bite wounds rather move to a mouse-free area because of their dedication to their eggs. US Fish and Wildlife Service is working on eradicating mice from Midway, but having lived with them for thousands of years I think we all know how well that will work out.

Mouse attack victim (Audubon)

This week's information comes from the US Fish and Wildlife Service and the National Audubon Society 

Species of the Month- Black Cottonwood

It’s May so why is it snowing? That’s not snow floating in the breeze and accumulating on the roads, it’s the seeds of the black cottonwood tree. Like dandelions, the black cottonwood’s seeds are attached to a white feathery substance. Allergy sufferers throughout the west lament this time of year because of the cottonwood snow.

Scientific name: Populus trichocarpa

Kingdom: Plantae (plants)

Class: Magnoliopsida (dicots)

Order: Malpighiales

Range: Southern Alaska to northern Baja California east to western Montana and Alberta

Habitat: Riparian woodlands, moist areas

Lifespan: 70 years on average

Diet: Sunlight, carbon dioxide, water, and soil minerals         

Predators: voles, mice, rabbits, deer, elk, slugs, insects (moths, tent caterpillars, borers), fungi

Conservation Status: No special protection

Other Information: Black cottonwood is the largest western hardwood species. Every cottonwood I’ve seen is near water. Not surprising then that it takes forever for the wood to season before you can burn it. Because it is usually found near water, it can be a great tool to use if you get lost in the woods. Look for the tall tree with glossy leaves and follow the water downstream to civilization. It is used to make pulp and veneers. In addition to windborne seeds on those cotton tufts, cottonwood also reproduces through cloning. Stumps will sprout and cutting can grow into a new tree.

This week’s information comes from USDA’s Forest Service Silvics Manual. Lifespan information come from Northern State University.

This cottonwood is estimated at about 140 feet tall

The glossy leaf. Note in the background the lighter underside of the leaf

A look at the thick bark

USDA: https://www.na.fs.fed.us/spfo/pubs/silvics_manual/volume_2/populus/trichocarpa.htm

Northern State: https://www3.northern.edu/natsource/TREESA1/Easter1.htm 

Urban Ecology

When most people think of nature, they think of pristine wilderness or a patch of woods somewhere in the country. But nature is all around us, even in cities and towns. Large chunks of the natural world often go unnoticed simply because they are so familiar as to become invisible. This week Nature Minute introduces you to the wonderful world of urban ecology. For ecology purposes, "urban" refers to any developed area, not just inner cities.

            Most of the wild mammals you meet in our neighborhoods are considered a nuisance. Raccoons are infamous scavengers that thrive on garbage can buffets, while mice and rats make our homes their own.  Even charismatic animals like deer (eating our gardens and crashing our cars) and bears (raiding or trash cans and generally being scary) are a nuisance when they leave “the wild” and come into our communities.

Black-tailed deer in my back yard

            Then there are the animals you don’t meet. Crows and pigeons are all over the place yet we overlook them because they are so common. Coyotes have adjusted to our cities and towns, yet remain under the radar, earning them the name “ghost dogs”. I see their scats all the time, but I’ve only seen three coyotes in ten years.

            Squirrels, chipmunks, and many species of songbird live in our yards, but they live so close to our homes many people don’t even consider them when thinking of examples of wildlife. They may be used to being around people but they certainly aren’t tame.

Eastern gray squirrel outside my apartment

            Insects and plants also fall into the realm of the wild, though very few people would ever call a beetle, worm, or shrub wildlife. However, these organisms are the base of the food chain and in the absence of garbage, sustain the larger critters that share our neighborhoods.

Baby barn swallows nesting in a hole in wall of my house

            How can you make our urban areas more hospitable to wildlife? The National Wildlife Federation’s Certified Wildlife Habitat program is one way to start making a difference. Turn your yard into habitat by providing food, water, shelter, places to raise young, and using sustainable practices. In many areas, habitat is severely fragmented, and by turning your yard into a habitat island you can help wildlife move from place to place. Learn more at www.nfw.org or by asking me!

Animal Attraction

In a previous episode of Nature Minute we talked about porcupine love. With Valentine’s Day right around the corner it’s time to revisit the subject.

In the human world, success is usually measured in money and power. In the natural world, success is measured by passing on genes to a new generation. Darwin proposed evolution as natural selection by survival of the fittest. Those best equipped to survive their environment will have the most offspring, in theory.

There are two ways in nature to ensure that your offspring will survive to produce offspring of their, furthering your own genes. The first is a high reproductive rate (fecundity) with little to no parental care. The second is lower fecundity with a high rate of parental care.

Some examples of high fecundity animals are insects, which lay thousands of eggs, and mice, which may have multiple litters of a dozen or more in a single year. Surviving mouselings reach sexual maturity at a very early age and have babies that are older than their aunts and uncles. Many plants fall into this category also. Think of how many wishes you’ve made with dandelion seeds. Or if you are like me, think of how many mornings you woke up to a yard full of dandelions that weren’t there the night before.

Lower fecundity breeders are typically larger than high fecundity breeders (this is a general rule, but there are exceptions of course). We fall into this category, along with whales and elephants. We all have a relatively long gestation period (40 weeks for people, 20 months for elephants) and births are commonly single. Sexual maturity takes years to reach and mothers do an excellent job of caring for their young.

Just as there are two ways of breeding, there are also two ways of breeding- monogamy and promiscuity. Monogamy is what we think of in human relationships, a pair mating for life. Bald eagles and barn owls are monogamous.

Promiscuity can be either male or female. Male promiscuity is very common in the natural world (and humans too). A successful male has many offspring, but why should he limit himself to a single female? In these situations, frequently a dominant male will have a harem of females to mate with. Elk and bison are great examples. Going back to a previous Nature Minute on the elk rut, we learned that young males will challenge the older dominant male for the right to mate.

Elk rut, photo by Tom Bartel

Female promiscuity is way to confuse males. In some species, a male will kill any young that are not his own. He wants his own genes, and not someone else’s, to be passed on in perpetuity. To counter infanticide, in some species the female will take multiple mates. Since no one is really sure who the father is, all males assume fatherhood and are unlikely to kill any young since it very well could be their own. It is even possible for all of them to be the father. Bees, hedge sparrows, and garter snake females will all take multiple mates.

In the human world, typically a boy will ask a girl out on a date. Females hold all the power. The same is true in the animal world in many cases. Males will put on a courtship display or perform a courtship ritual, hoping to catch the attention of a lucky lady. Prairie chickens have a lek, which is similar to a middle school dance, but the stakes are higher. Boys on one side, girls on the other. The males strut their stuff and the females pick out their favorites. After it’s over, they all go back to their home territories. Usually there is some desirable trait that females are looking for that demonstrates the male’s fitness (as is “survival of the fittest”, not like a fitness test in gym class). It can be brightly colored feathers, awesome dance moves, the loudest croaking, huge antlers, or any number of other things. The male with the best traits gets to pass those on to the next generation through his genes.

Greater prairie chicken lek, photo by Adrian Binns

So what did we learn today? When it comes to love, people are still pretty much animals. It’s ladies’ choice, and the guys really don’t care as long as she says yes.