Resource Ramblings 2006-05
First Bison Calf of the Season
The first bison calf observed for the 2006 season was on April 4, with “first sighting” honors going to Sabrina Henry, Jason Devcich and Jamie Chronert, who all observed the male calf along NPS 5.
Bison have an average gestation period of 9 months (270–300 days). Calves are born singly beginning in April, peaking in May, with a few stragglers born as late as October. Bison calves typically weigh between 30–40 pounds at birth. At Wind Cave National Park, calves attempted to stand within 10 minutes of birth and began to walk by 20-35 minutes. By 15-45 minutes, they began to nurse and may run by 1.5 hours after birth.
Calves are born with a “cinnamon” or “milk-chocolate” coat. Between 5-12 weeks of age, the calves start to molt, and you may see a calf with a dark brown face and “cinnamon” body. By 10-18 weeks of age, most calves will have completed the transition to the dark brown or black coat seen on, older bison.
Mean nursing time decreases as the calves age, so weaning occurs gradually. At Wind Cave National Park, if a cow becomes pregnant during the July rut following the birth of her calf, she will continue nursing the calf until it has reached 9-12 months of age. If a cow does not become pregnant during the rut following birth, the barren cows continue nursing until the calf is 17-21 months of age. - Barbara Muenchau
Burrowing owls have arrived in full force this year. To date there have been 4 pair observed in the Red Valley prairie dog town, 2 pair in the NPS 5 prairie dog town and 1 in the Southeast prairie dog town. Bison Flats, Research Reserve and Sanctuary prairie dog towns have yet to be examined.
Burrowing owls (Athene cunicularia) typically arrive in the Park in April from wintering grounds in Texas and Mexico. They are a small ground-dwelling owl, about 9-11 inches in height and weigh around 8 ounces. They require underground burrows and in our area most often use previously excavated burrows of prairie dogs, preferring areas with little vegetation. They line the nest burrow with dung, which is believed to mask the scent of the owls from predators. If not disturbed, burrowing owls will choose the same burrow for nesting year after year (called nesting fidelity). The 3-10 white eggs are incubated by the female (males do not have a brood patch) and hatch after about 28 days. When the owlets are two weeks of age, they will emerge from the burrow, though are unable to fly until about thirty days after hatching.
Burrowing owls are recognized as a species in decline and are listed as “Endangered” in Canada, “Threatened” in Mexico and a “Species of Conservation Concern” in the United States. The decline of the species has mainly been attributed to the 99% decrease in prairie dog colony habitat, though indirect pesticide effects have also reduced potential prey availability. In South Dakota, arthropods account for the majority of food items, with small mammals the next most abundant prey item. Other food items include reptiles, birds and vegetation.
Please let the Biological Science staff of the Resource Management Division know if you observe burrowing owls in the Park. Additional observations will be necessary to verify if actual nesting is occurring. Barbara Muenchau
A New and Improved Plant List
Since the creation of Wind Cave National Park in the early 1900s, several park plant lists have been created. The earliest known list dates to 1936. A new and improved Wind Cave National Park plant species list has been completed and reviewed in preparation for input into the National Park Service NPSpecies database. This new list contains more than 1000 entries, and includes every plant species that appeared on earlier lists. Voucher specimens (pressed plants providing proof of occurrence) for each species are collected and stored in the park’s museum herbarium collection.
The current status of plant species is:
The Resource Management Division maintains the park list, which includes scientific names, common names, synonyms, voucher collection locations, status at the park, nativity, frequency of occurrence, and whether the species is considered weedy, a pest, a management concern or an exploitation concern. The list is updated as new species are discovered, and as vouchers are collected and catalogued. A reliable plant list is an essential tool that supports decision-making required as part of the park’s Vegetation Management Program. - Marie Curtin
Comments and feedback about Resource Ramblings are encouraged and can be made to Dan Foster, in person, or via email.
Did You Know?
The Field Milkvetch has a colorful flower which is often overlooked because it tends to grow hidden in the grass. Color can vary to reddish-purple. More...