Spring on the PrairieSpring on the prairie is a time of rejuvenation. Grasses like blue grama come out of winter dormancy and begin to shift nutrients from their vast root network to the shoots. Birds like the lark bunting return from their wintering grounds. Mammals like the swift fox give birth to pups in an underground den. In other words, spring means many different things to the many different forms of life on the prairie.
Migration to warmer climates is the way most birds deal with the extreme temperatures of winter. Burrowing owls, mountain plovers and ferruginous hawks fly great distances in the spring to stake their claim on the prairie again. Typically, one thinks of birds nesting in trees but what do they do if there are no trees? They nest on or in the ground. True to their name, burrowing owls use prairie dog burrows for nesting. Mountain plovers prefer areas of low vegetation and sometimes even bare ground for their nests. Ferruginous hawks will re-use nests from previous years but add fresh sticks. Nests of ferruginous hawks are often found on the ground, rocky outcrops and hills.
Birds have the ability to escape the cold winters and return in the spring. But what about those creatures that are less mobile, like the Great Plains toad? After digging a hole in the soil and slowing their metabolism to almost nothing they emerge as the spring temperatures warm the soil and the rains soak the ground. Breeding season for the toads can begin in April and the males will trill loudly to attract a female.
Several other species reproduce in the spring as well. In March and April both prairie dogs and black-footed ferrets breed, usually below ground in the safety and privacy of a burrow. Prairie dogs have a gestation period of about 33 days and by June the prairie dog pups begin to emerge. Black-footed ferret kits are born a little bit later and come above ground for the first time in July. Contrary to popular belief, prairie dogs only have one litter per year, as do black-footed ferrets.
Both bison and pronghorn have their breeding season in autumn but the gestation period is approximately 9 months, much longer than that of a prairie dog or black-footed ferret. After carrying a calf or fawn through the winter, the females will usually wander off from their respective herds to give birth on their own. Bison give birth to one calf whereas pronghorn usually have twins (except first time pronghorn mothers which generally have one fawn). Bison calves are reddish-orange in color and the precocious youngsters quickly form nursery bands with other calves. Pronghorn fawns, also called ‘kids’, are quite drab in color compared to their mother and odorless to foil any predators. The ‘kids’ will spend much of the next 3 weeks bedded down and their mother will return every few hours to nurse. If there is danger, the fawns will press their body close to the ground and remain motionless, making them very difficult to locate. The fawns begin scampering about after 3 weeks and then join the rest of the pronghorn herd.
For all prairie creatures, spring is an essential part of the life cycle that is woven together in many ways. The green grasses provide forage for the pronghorn, bison and smaller mammals, such as prairie dogs and mice. The sudden increase in rodent numbers (because of breeding season) is the food that fuels black-footed ferrets, ferruginous hawks and swift fox. Wildflowers attract insects that rapidly reproduce, providing a high protein food source for burrowing owls and mountain plovers to feed their growing chicks. All of the successes and failures of spring set the stage for the next season; summer.