The Hagerman mole is no mo'
Most people's reaction to moles is a negative one. They're pesky animals that burrow in your lawn and make ridges as they dig their tunnels. If you’ve had mole holes in your yard it was probably not while you were living in Idaho. In this state they are not common, and only a few specimens are in museum collections. The mole that is found in Idaho today is the Coast Mole, Scapanus orarius. As the name suggests it is more commonly found along the coast. Most of the records of this species place it in Oregon on the coastal side of the Cascade Mountains. The distribution of the animal does extend across the northern part of Oregon and then crosses the Snake River into Idaho. The Idaho records are as far east as this species gets.
Moles are highly adapted for digging and this can be seen in their skeleton. The arms stick out to the side of the body so that the animal almost swims through the soil by doing the breaststroke. This digging requires powerful chest and arm muscles. The upper arm bone or humerus, bones of the forearm, ulna and radius, as well as the hand, are stout and show prominent ridges and processes where muscles attach. The hand is broad with an extra bone for support and the claws are strong. The distinctive shape and structure of these bones makes them easy for a paleontologist to identify.
Although moles are master diggers and produce extensive tunnel systems, they are still limited to where they can live. Since they live most of their life underground, they can only live where the type of soil permits burrows to be dug. If the soil is too hard, soft or wet, then it may not be possible to dig a burrow or it may collapse or fill with water. Certainly many parts of southern Idaho with its thick layers of basalt resulting from numerous lava flows are inhospitable for moles and may be one of the reasons why they are not present in the south-central and southeastern part of the state. But thick extensive lavas are not as common in the southwest part of the state. Much of the geology of Owyhee County is composed of sands, silts and clays of the Glenns Ferry Formation, the same as found at Hagerman Fossil Beds, yet there are no moles in this part of the state today. Perhaps because this part of the state is a high desert with limited rainfall. While moles may not like soil that is too wet, they can't live in an area that is too dry either, as it may not support enough earthworms and insects to sustain a viable population of moles.