Category Archives: Prairie Animals

Patches of Fire and Habitat

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It’s been a difficult year for conducting prescribed fires so far – the wind seems to be blowing even harder and more consistently than in recent memory.  And that’s saying something, living in the Great Plains.

A couple of weeks ago, we were able to pull off one prairie management burn here in the Platte River Prairies.  The fire went well, and this week I took a quick walk through the burned area to see how the regrowth of vegetation was coming along.  It’s been a cold and dry spring, following a dry fall and winter, so plant growth has been slow, but things are finally starting to kick in.  Within the burned area, many plant species are a little behind their compatriots growing outside the burned area, but others are ahead.  Those that are behind are the species that were already starting to grow when the fire came through – those species had to start again, so are behind schedule.  The species that are further ahead in the burned area are those that are taking advantage of the warmer soil and have either germinated or emerged faster than those in the cooler soil of unburned areas.

Regrowth in sand prairie burned a couple weeks ago. The wildflower in the foreground is shell-leaf penstemon (Penstemon grandflorus).

Regrowth in sand prairie burned a couple weeks ago. The wildflower in the foreground is shell-leaf penstemon (Penstemon grandflorus).

Regardless, plants are growing well in the burned area.  That’s good, because cattle will arrive within the next week or so, and we want the burned area to be particularly attractive to those grazers.  One of the major objectives of our fire was to concentrate grazing in one portion (the burned patch) of the prairie this season, leaving the remainder of the pasture with much less intensive grazing.  Hopefully, the result will support our efforts to create a variety of habitat patches across our prairies, and to shift the location of those patches from place to place each year.

The patch we burned this spring has had no fire and very little grazing over the last couple of years.  Last year, it had tall vegetation and abundant thatch – conditions that favor a certain set of plants and animals, but not others.  This year, it will have very little thatch and the vegetation will be short in stature because of season-long intensive grazing.  Next year, it will begin a multiple season recovery period from that fire and grazing until it is burned again sometime down the road.  (You can read more about patch-burn grazing here.)

Burning a different patch of prairie each year helps ensure that a mixture of habitat types is always available and most or all wildlife and invertebrate species can find the habitat they need.  Our prairies usually have a patch of very short habitat, several patches in some stage of recovery from intensive grazing, and some areas that are tall and very lightly grazed – or ungrazed.  Some animals will follow those habitat patches across the landscape.  Others will go through boom and bust periods within one portion of a prairie, depending upon what conditions they thrive best under.

Because we’re always changing the location of habitat patches, plant species also experience changing conditions from year to year.  This means that some species flourish one year, but may have to wait a few years before those favored conditions return.  In the meantime, other plant species will find success.  Constantly changing conditions help ensure that no group of species becomes too dominant, but that all species can survive and maintain a place in the plant community.  Our long-term data has shown the our plant communities have stable to increasing plant diversity under this kind of management, and we’re not seeing any plant species disappear.

This burned patch makes up between a third and a fourth of a 110 acre management unit in our Platte River Prairies. Burning only a portion of each unit each year helps ensure good wildlife habitat and changing growth conditions for plants, but also helps avoid catastrophic impacts on species vulnerable to fire.

This burned patch makes up between a third and a fourth of a 110 acre management unit in our Platte River Prairies. Burning only a portion of each unit each year helps ensure good wildlife habitat and changing growth conditions for plants, but also helps avoid catastrophic impacts on species vulnerable to fire.

Another benefit of burning only a portion of our prairies each year is that it helps us avoid catastrophic impacts on plant and animal species that are negatively impacted by fire.  Invertebrates that overwinter above ground, for example, can be destroyed by an early season fire.  Growing season fires can kill animals (invertebrates and vertebrates) that are unable to escape by leaving the area or retreating underground.  These kinds of impacts are somewhat unavoidable, regardless of the season of fire, but by burning only a portion of our prairies, we can try to restrict impacts to a relatively small proportion of the population of each species, allowing the majority of individuals to survive and recolonize the burned patch over time.  Burning an entire prairie, especially in highly fragmented landscapes in which recolonization is unlikely, can result in completely and permanently obliterating vulnerable species from a site.

Hopefully, the wind will pause a few times during the remainder of the spring, and we’ll create a few more burned patches in our prairies.  If not, we’ll try to create patches of short habitat by haying or by temporarily fencing cattle into an area to knock vegetation height down.  We’ve found that all three methods (burning, haying, temporary enclosures) can create a patch that attracts livestock grazing afterward – and therefore pulls that grazing off of other portions of prairie.  There are lots of ways to create patchy habitats, and none are necessarily best.  As long as there is always a mixture of habitat types across our sites, we feel pretty good about our management.

Hopefully, the species living in our prairies feel pretty good about that management too.

 

Darn Gophers…

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19

People who live in the country tend to view “gophers” in much the same way city people view rats. Suffice it to say, neither animal is particularly popular.

Much of the time, when farmers, gardeners, or groundskeepers are complaining about “gophers”, the animal in question is actually a ground squirrel – and around here it’s usually a thirteen-lined ground squirrel. Although they are beautiful little animals, thirteen-lined ground squirrels have run afowl of humans because their preferred natural habitat of short-cropped grassland is very similar to that found in many yards, baseball diamonds, gardens, and crop fields. When ground squirrels move into those human-built habitats, their burrowing and feeding behavior tends to get them in trouble.

 

Thirteen-lined ground squirrels are very attractive animals - unless they're eating your garden plants or digging holes in your landscaping.

Thirteen-lined ground squirrels are very attractive animals – unless they’re eating your garden plants or digging holes in your landscaping. There are actually two ground squirrels in this photo – can you find the second one? Click on the photo to see a larger and sharper version of it.

Thirteen-lined ground squirrels (Ictidomys tridecemlineatus – formerly Spermophilus tridecemlineatus) are found throughout much of central North America. They are 5-7 inches in length, not counting their 4-6 inch tail. Their name comes from the combination of light and dark stripes that run lengthwise along their body. The lines of spots within the darker stripes are particularly striking.

Thirteen-liners have a high-pitched call – among others – that sounds much like a bird. In fact, it took me several years to figure that out. I know my grassland bird calls very well, but couldn’t for the life of me figure out what bird species kept calling but never flushing as I moved in to investigate. I finally realized it wasn’t a bird at all, which made me feel both embarrassed for being so badly wrong and satisfied that I wasn’t woefully ignorant of some common bird call.

There are several kinds of burrows made by thirteen-lined ground squirrels, each with its own purpose. Nesting burrows can be 15-20 feet long, with multiple entrances. Hiding burrows are usually scattered around nearby to provide a quick escape, but those burrows are typically very short and have only one entrance. During the winter, the ground squirrels hibernate in burrows that extend below the frost line and the entrance is plugged up until the ground thaws enough in the spring that the hungry inhabitant can burrow back out again. In all cases, thirteen-lined ground squirrels disguise the entrances of their burrows by scattering the excavated soil away from the hole itself.

Ground squirrels are themselves well camouflaged, and help disguise their burrows as well, by spreading soil out away from entrances.

Ground squirrels are themselves well camouflaged, and help disguise their burrows as well, by spreading soil out away from entrances.

Thirteen-lined ground squirrels eat seeds throughout the year, but favor them most in the fall as they prepare for hibernation. During the spring and summer, they consume green leaves, fruits, and flowers from many plants, but are also fairly significant predators, feeding on worms and insects (especially caterpillars, beetle larvae, and grasshoppers) as well as small vertebrates. In fact, grassland bird studies have shown thirteen-lined ground squirrels to be a very significant predator of both eggs and young birds in some prairie landscapes.

In my part of the world (east-central Nebraska), there are two species of ground squirrels, which are differentiated by both habitat preference and coloration. While thirteen-lined ground squirrels have distinctive striping and prefer to live in very short vegetation, Franklin’s ground squirrels are found in tall grass and are unstriped.  Franklin’s ground squirrels are rarely seen, but we spot enough of them in our Platte River Prairies to assume they must be fairly common here. I’d like to know much more about their habits and needs because they are a species of conservation concern – especially in more eastern tallgrass prairie regions.

While Franklin’s ground squirrels are fairly uncommon in many places and difficult to find when they do occur, thirteen-lined ground squirrels are very common and abundant – much to the chagrin of those people who find themselves at odds with them. Thirteen-liners enjoy the more intensively grazed portions of our prairies, and seem able to find new patches of grazed prairie as we change the location of that habitat type through time.  I’ve often wondered whether an individual ground squirrel actually relocates each year to keep up with those shifting patches of short-cropped prairie, or if populations just increase (and/or become more visible!) where our grazing is most intensive each year.

Ground squirrels are important prey for many of the larger predators in our prairies, including hawks, coyotes, snakes, and badgers. In fact, their popularity as badger food can compound the hassles associated with having thirteen-lined ground squirrels living in cultivated or landscaped places. In our own prairie seed nursery, ground squirrels enjoy living and running around in the plots and mowed trails between them – and we can (mostly) live with whatever damage they cause. However, the giant holes created by badgers digging ground squirrels out of their little burrows are a lot harder to ignore.

Darn gophers…