Chirpless: Camel Crickets

camelcricket

Camel crickets (Ceuthophilus sp.) enjoy hanging out with humans. Perhaps you provide shelter to some in your garage or basement. These insects lack one major cricket trait though – chirping. Sound production should allow camel crickets to find each other in a dark cave or crawlspace. So, why no chirps?

A Chirp Mystery

One possible reason for the lack of chirps is a high risk of predation. In other species of crickets, those who call more or longer often end up as a snack. 1, 2 While I would hope camel crickets are relatively safe from bats and birds in your basement, spiders and mice are the crickets’ major predators. Both possess a solid sense of hearing.

Many crickets have parasites who also seek hosts by sound. Chirps attract female crickets, but they also draw mama parasites searching for a cozy spot to lay eggs. The developing parasitic larvae eat the cricket from the inside, exploding out of its body as they grow. Crickets in areas with these parasites quickly evolve “chirplessness.” Do camel crickets need to worry about these “Alien” chest-bursting scenes? While they do have a doozy of a parasite (an intestinal parasite that weakens the cricket enough to ensure predation), the infections are not related to sound production.

Perhaps camel crickets simply lost their physical ability to chirp. Most crickets produce sound by rubbing their wings together. Camel crickets, though, don’t have wings. In a basement, flying is probably not the most effective means of transportation.

The Scent of a Cricket

So, how do camel crickets find each other without sound? One word: pheromones.

Pheromones are used by many cricket species to indicate dominance, reproductive readiness, and location. Camel crickets release a scent that causes them to congregate. Researchers determined the pheromone is unrelated to reproduction since juveniles move toward the scent too. Nagel and Cade3 think the pheromone prevents camel crickets from drying out. We do know the antennae detect these pheromones. In a rather disturbing experiment, researchers found that camel crickets don’t aggregate when their antennae are lopped off.

 

  1. Baily, W.J. & Haythornthwaite, S. (1998). Risks of calling by the field cricket Teleogryllus oceanicus: potential predation by Australian long-eared bats. Journal of Zoology. 244(4) 505-513.
  2. Hedrick, A.V. (2000). Crickets with extravagant mating songs compensate for predation risk with extra caution. Proceedings of the Royal Society B 267(1444) 671-675.
  3. Nagel, M.G. & Cade, W.H. (1983). On the role of pheromones in aggregation formation in camel crickets, Ceuthophilus secretus (Orthopter: Gryllacrididae). Canadian Journal of Zoology 61(1).
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Purring Predators

flea_byJMLandin

As agriculture took hold in Middle Eastern societies about 10,000 years ago, archeological evidence of cat domestication appears. When humans began storing grain, any rodent-killing animal was a benefit. But the presence of cats didn’t spread along with agriculture. Egyptians may have revered cats, but other civilizations used weasels or snakes to limit mice. In the painting “Lady with an Ermine” by Leonardo da Vinci, the weasel may symbolize purity or the young woman’s last name (similar to the Greek word for ermine). With all due respect, however, I think the animal may have just been the lady’s pet; weasels were more common pets than cats at that time.

ermine

Cats may have been popular in Egypt during the heyday of the Roman Empire, but Greeks and Romans kept weasels as their rodent-killing pets. Cats joined European families around the fourth century but were relatively uncommon until the 1600s (1).

Nowadays, of course, cats are popular pets and internet memes. Their omnipresence is also a major cause of concern to ecologists and bird lovers. In a 2013 research article, Loss et al. estimated our purring pets (and their feral cousins) kill about 2.5 billion birds and 12 billion rodents each year in the U.S. alone (2).

P.s. The adorable cat who posed for this painting is our own 18-year old feline princess, Flea. She’s killed exactly one bird in her life, a fledgling finch who accidentally flew into her mouth. Flea didn’t even bite down; the little bird panicked to death.

  1. The Oxford Handbook of Animals in Classical Thought and Life. G.L. Campbell. 2014. Oxford University Press.
  2. Loss, S.R. et al. 2013. The impact of free-ranging domestic cats on wildlife of the United States. Nature Communications 4:1396.

Sometimes you DO choose your family (of geese)

gosling

What would happen if an adorable 3-day old gosling was placed between two wire enclosures, one containing a sibling, and one containing a same-age gosling from another clutch? Would the baby bird recognize its brother or sister and patter over to its relative?

The answer: yes… at least as often as dentists recommend sugarless gum*. In four out of five trials, the little puffball sidled up to its sibling rather than a stranger’s young’un.

There’s one catch. The youngest goslings (ages 3–9 days) prefer groups. Even if it’s a group of unfamiliar goslings, the little bird almost always waddled over to an unknown group rather than a single relative. By 15 days old though, the youngsters reliably reunite with their kin, no matter how small their family.

p.s. I created this image at an awesome carbon dust workshop, coordinated by GNSI-Carolinas, this weekend. Marlene Hill Donnelly from the Chicago Field Museum was our fearless instructor – she’s wonderful!

*Radesäter, T. 1976. Individual sibling recognition in juvenile Canada geese (Branta canadensis). Canadian Journal of Zoology, 54(7): 1069–1072

Signs of Spring: Robins and Lawn Mowers

robin2

Two robins (Turdus migratorius) hopped through the yard this week – spring is on its way. The sound of lawn mowers now drift through the air, confirming the avian prediction. Shockingly, these two very distinct signs of warming weather are actually related, according to a backyard research study conducted in 1979.

L.A. Eiserer conducted a series of scientific (well, somewhat) studies examining the impacts of lawn mowing on robin-hunting behaviors. Robins spend more time foraging when grass is short, especially just after it has been mowed.

So is it the mowing or the height of the grass that impacts robin behavior? Eiserer mowed his lawn to two different heights, 2.5 and 4.5 inches. (I wonder if his neighbors complained.) The robins spent 10x as much time in the shorter patch. Apparently, the birds eat different foods when exposed to different heights of grasses. In short grass, robins go for worms; in longer grass, they pluck small insects off the blades. The short-grassed hunting grounds may just be more efficient for finding a heartier meal.

But that doesn’t discount the act of mowing. Observations over the same time of day show the birds prefer hunting in a freshly mowed yard rather than the day after. No difference in grass height, but perhaps the act of mowing disturbs invertebrates, allowing for a more successful hunt.

Overall, I miss the days when a researcher could sit on a suburban porch and time how long a couple of robins spend looking for food. As I struggle to teach my students how to think like scientists, reading a study like this makes me long for the good old days.

 

Eiserer, L.A. 1980. Effects of Grass Length and Mowing on Foraging Behavior of the American Robin. The Auk. 97(3) 576-580.

G’night, Groundhog

groundhog

It may seem like an odd time for a post about groundhogs (Marmota monax) – a couple months early, right? But I think now is an even better time. Groundhogs (a.k.a. woodchucks or whistle-pigs) are considered one of the few true hibernators of winter.

What about bears? This is where we get into an issue of degrees (pun totally intended). Bears lower their metabolism and body temperature, and by doing so, conserve energy in winter when food supplies dwindle. Normally, bear body temperature is ~98.6⁰ F (37⁰ C), just like humans. In torpor (like a mild hibernation), their body temperatures drop to 86⁰ F (30⁰ C).

The groundhog, in comparison, can lower its body temperature from 99⁰F to 37⁰ F (5⁰ C)! That’s hibernation! It allows the rodent to decrease its energy use to 1% of normal.

Think of torpor and hibernation like changing the temperature settings in your house. In torpor, you drop the settings a couple of degrees while you’re at work. Hibernation is like shutting temps way down, just enough to keep the pipes from freezing, while you head to Florida for a month-long vacation.

Some scientists study how the groundhog accomplishes this marvelous feat. Figuring out those specifics could impact healthcare and space travel for humans.

p.s. Some animals hibernate in the summer, but this is called aestivation (est-eh-VAY-shun).

p.p.s. This watercolor is now available on RedNewtGallery’s Etsy site. (yay!)

Winter’s “Toasted Marshmallow” Egg Case

MantisEggs

This “toasted marshmallow on a stick” is the egg case of a Chinese Praying Mantis (Tenodera sinensis), containing hundreds of developing youngsters. The eggs overwinter in this protective case until the spring’s warm weather triggers the eggs to hatch into tiny nymphs (mini-mantids). Nymphs grow into adults who enjoy their summer, snacking on any and all insects who cross their paths. In the fall, Praying Mantises mate, lay their eggs, and pass away.

A female mantid’s work may all be for naught if a tiny parasitic wasp interferes. The mantis lays her eggs in a frothy matrix that hardens around her offspring; but this mini wasp (sporting a ridiculously long ovipositor and rear legs that look like the mantids’ front legs) can lay her eggs inside the mantis case before it hardens. Since the wasps hatch first, they’ll use the mantis eggs as food.

Thanks to Mike Dunn (Roads End Naturalist) who recently presented a guide to winter wildlife – tracks, chew marks, and insect sign. Not only was I awed by his amazing photos, Mike also brought samples of all sorts of wintertime insect egg cases (including this one), cocoons, nests, tracks and galls.

A World Without Bunnies

rabbitsI hate to break it to you, but there’s really no such thing as a bunny.

Among rabbit-like animals, we have “rabbits”, “hares”, and “pikas” (by the way, NONE of these animals are rodents – rabbits and rodents diverged fifty million years ago).

Rabbits are generally smaller than hares – slightly shorter ears too. The big difference, though, occurs at birth. Rabbit young are born after a much shorter pregnancy (30 days rather than 42 days) and the babies are less developed. Just-born rabbits (“kittens”) haven’t grown any hair yet, whereas the hare babies (“leverets”) are furry.

Rabbits also enjoy a cozier household than hares. Rabbits live in underground burrows, called warrens (check out this concrete cast of a rabbit warren).  Only the Cottontail Rabbit (Sylvilagus floridanus) stays above ground like hares.

If you’re wondering how those poor Cottontails deal with cold winter weather, see this neat Urban Wildlife study by the Lincoln Park Zoo.  And while we’re on the subject of urban rabbits, read how city-rabbits are trading their sprawling suburban homes for compact city flat.