Early blooming trees like Elms and Maples produce a bonanza of high energy seeds, greatly coveted by Eastern Gray Squirrels (Sciurus carolinensis). Their frenetic activity high in the trees is a common sight in early spring. In some areas, they appear to have an affinity for Slippery Elms (Ulmus rubra), and can be seen selectively foraging there while ignoring neighboring Winged Elms and Maples. In one such case, pictured below, the squirrels appear to be chewing off fairly long portions of the terminal ends of twigs, littering the road below with the pruned debris, and apparently wasting large numbers of seeds.
However, a closer look through binoculars revealed a possible motive for this seemingly senseless activity. Most of the Slippery Elm seeds seemed to be concentrated on the terminal portions of the outer twigs; the squirrels could not reach them safely, as the twigs were too thin and unstable to support their weight. So some of them were chewing off the twigs at a spot that they could safely reach and then attempting, usually unsuccessfully, to grab the cut twig. One squirrel was observed to hang on to a cut twig, only to mishandle it a few minutes later after eating many of the seeds. Below is a closer look at one of the cut twigs. Notice the white pith bared at the end of the twig where it was chewed off by the squirrel.
Slippery Elm seeds (called samaras) are round or oval shaped and have smooth wings that surround the central seed. See below, with samaras on ruled notebook paper to gauge their size.
Below, the Slippery Elm samaras are contrasted with those of the Winged Elm (Ulmus alata). Clearly, the Winged Elm samaras are much smaller and are more difficult for the squirrels to handle, with a smaller energy reward for the effort expended. Notice their fuzzy margins and the hooks or claws at the end of the samaras.
A closer view with better contrast shows the very fuzzy margins of the Winged Elm samaras compared with the smooth margins of the Slippery Elm samaras.
Most of the year, Eastern Gray Squirrels are obsessed with stashing acorns and nuts in caches. However, the abundant Spring tree seeds allow the squirrels the opportunity to increase their energy stores early in the year. They eat the small seeds where they find them because they do not have cheek pouches to carry the seeds for storage.