28.0°

Three road-kill porcupines appeared overnight on the North Douglas Highway last week, a reminder it's mating season for these big rodents. Males are on the prowl, tracking hints of scent to find females in heat.

Most people know how porcupines mate (very carefully), but these familiar critters have some surprising aspects to their reproduction.

During the fall mating season males expand the size of their range considerably searching for females, and that can put them on the highway. Biologist Uldis Roze, in his outstanding book The North American Porcupine, describes one radio-collared male who expanded his range from 50 acres to 250 acres in late September.

Females provide a scent that signals they are coming into estrus, and that scent is on their bodies and in their urine. Porcupines spend much of their lives in trees, and I imagine a female peeing into the wind from the top of a tree can broadcast an effective come-hither signal. A female porcupine is in estrus just once a year, for about 12 hours. That's a narrow window, but clearly porcupines find each other. When a male finds a female who isn't quite ready he guards her, checking frequently to see if she's receptive. I've seen this a couple times.

I was picking high bush cranberries near Basin Road one fall and came across a pair of porcupines preoccupied with each other. One - the male I assume - was fixedly following the other around, but she wasn't interested. He would sidle up next to her and she'd amble off, and a few times he waddled up ahead and tried to herd her back down the trail. She'd nibble on plants and he'd try to get close, then she'd move away. Evidently patience is part of the courtship.

That female was relatively indifferent, but that's not always the case. I was deer hunting on North Douglas and I heard a loud squealing, much like the sound a deer call makes. I figured I was either on to a deer or another hunter blowing a call. I carefully approached the sound and discovered two porcupines in the low branches of an alder. One seemed to have the other cornered, and the one on the end of the limb was doing most of the squealing. I've since heard porcupines yelp, squeal, bleat, mutter and hum, but that was the first time.

After reading Roze's porcupine book, it seems apparent that in both these cases males were pursuing females. Males tend to find females before they are ready. Sometimes more than one male finds a female, and if that happens, they fight. Roze describes finding his radio-collared males limping around after mating-season fights with wads of hair and fur torn out and quills in their faces. He writes that generally the biggest and heaviest porcupine wins.

When the male finds a potentially receptive female, he tries to spray her with urine. Some researchers describe a major soaking. If she's not ready she shakes it off. If she is ready she takes the wetting, then she curls her tail over her back, covering her quills.

Porcupines have an extremely long pregnancy, about 210 days. That's on par with deer, and longer than almost any small mammal. It's particularly remarkable considering porcupines are rodents, animals known for their rapid gestation. Rats gestate for three weeks, marmots for a month, and porcupines for almost seven months. Half the weight gain of the fetus occurs in the first sixth months, and then the fetus rapidly doubles in weight the last month, in April or May. The baby is about one pound at birth, roughly the same weight as a newborn bear cub. It will double in weight again in the first few weeks, nursing and eating green spring plants.

Porcupine moms give birth to just a single baby a year, called a porcupette. That's also surprising considering that other rodents generally all bear large litters with each pregnancy. The quills are not a problem for the mother at birth as the porcupette is encased in a little sack called a caul. The quills are also soft at first and harden within an hour. I've seen almost-newborn porcupines, even watched one nursing, and they are fully loaded with tiny, needle-sharp quills.

Drivers should watch out for amorous porcupines over the next few weeks. They don't look both ways when they cross the street, even when they aren't hot on the scent of a potential mate.

• Riley Woodford is a writer for the Alaska Department of Fish and Game. He produces the "Sounds Wild" radio program and edits the magazine Alaska Fish and Wildlife News: www.wildlifenews.alaska.gov.