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Hubbard Fellowship Post – Grasshopper Mice

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This post was written by Jasmine Cutter, one of our Hubbard Fellows.  Jasmine has written earlier about her independent research project looking at small mammals (or s’mammals, as she calls them) in our Platte River Prairies.  All photos are by Jasmine unless otherwise credited.

S’mammal Spotlight: the Fearsome Northern Grasshopper Mouse

While I finish up the data entry for my independent project on small mammals, I thought it’d be fun to share some more information about some of the s’mammals out in our prairies. Some of them are really, especially awesome, and hopefully knowing a little more about them will elucidate why we think they’re worth studying!

The northern grasshopper mouse. Note the big eyes and ears.

The northern grasshopper mouse.  See the note at the end of this post about how this photo was taken.

I thought I’d kick off this series with one of my favorites, the northern grasshopper mouse (Onychomys leucogaster). There is no other way to describe this critter except beefy. This is a mouse made for fighting, for pouncing, for striking fear in the hearts of the other lil s’mammals (I haven’t obtained any critter statements about the last part, but if I was pocket mouse-sized, I’d be wary). They are a handful to work with – very aggressive, and surprisingly agile. They’re able to shrink out of pretty much any corner I try to limit them to, and their pointy carnivorous teeth ensure that I am very aware of the distance between my fingers and their mouth!

If you’re wondering if you’ve seen one, northern grasshopper mice have big eyes, big ears, and relatively short tails that are consistently about 42 mm long (Mike and I measured many grasshopper mouse tails). The majority of them are silky gray-brown on top and white below, though there are a few whose backs are more cinnamon-y than gray. Juveniles tend to be lighter colored. Most of the grasshopper mice I caught were approximately the size of my fist, maybe a little smaller, about 33-45g (for reference, pocket mice are generally 8-12 grams).

cute lil grey guy. I would guess this one is on the younger side of things. Its fur has some of that downy, juvenile look to it. [good ones for the disclaimer? When I open a trap, I gently plop the critter into a bag in order to minimize handling exposure. I can weigh, identify and sex the critter while it’s in the bag. It’s safer for me, and the animal is only in there for a few seconds to a minute.

Cute lil grey guy. I would guess this one is on the younger side of things. Its fur has some of that downy, juvenile look to it. DISCLAIMER: When I open a trap, I gently plop the critter into a bag in order to minimize handling exposure. I can weigh, identify and sex the critter while it’s in the bag. It’s safer for me, and the animal is only in there for a few seconds to a minute.

This is one of more cinnamon-y colored ones.

This is one of more cinnamon-y colored ones.

The impressive muscle mass of a northern grasshopper mouse is achieved by a largely carnivorous diet. True to their name, grasshopper mice consume a lot of grasshoppers, as well as other insects, and sometimes other mice, including others of their species. Allegedly, grasshopper mice stalk their prey and will emit a shrill cry before attacking. It is thought that they tend to have a longer period of maternal care than most mice (which isn’t saying much) so that young grasshopper mice can be taught to hunt. Ideally, I’d like to camp out by their burrows in the spring so that I can hear them sing and see their fearsome predatory skills in action.

This is probably one of the youngest-looking grasshopper mice I found. It is fairly small, its fur is still more downy than silky, and its head/eyes to body ratio makes me think it's pretty young. Also it wasn't very good at being elusive or aggressive compared to most, so hopefully mom is still giving it some lessons! [The clip on its tail is attached to my mouse scale. While it is undoubtedly a little uncomfortable, there is no permanent damage. Using the clip means I am touching them less, and speeds up the photo taking process so they can be released faster!] This is probably one of the youngest-looking grasshopper mice I found. It is fairly small, its fur is still more downy than silky, and its head/eyes to body ratio makes me think it's pretty young. Also it wasn't very good at being elusive or aggressive compared to most, so hopefully mom is still giving it some lessons! [The clip on its tail is attached to my mouse scale. While it is undoubtedly a little uncomfortable, there is no permanent damage. Using the clip means I am touching them less, and speeds up the photo taking process so they can be released faster!]

This is probably one of the youngest-looking grasshopper mice I found. It is fairly small, its fur is still more downy than silky, and its head/eyes to body ratio makes me think it’s pretty young. Also it wasn’t very good at being elusive or aggressive compared to most, so hopefully mom is still giving it some lessons! [The clip on its tail is attached to my mouse scale. While it is undoubtedly a little uncomfortable, there is no permanent damage. Using the clip means I am touching them less, and speeds up the photo taking process so they can be released faster!]

 

The underside of a grasshopper mouse. If you look closely, there's a faint orange circle on this one's chest, suggesting that I marked it on a previous week's transect.

The underside of a grasshopper mouse. If you look closely, there’s a faint orange circle on this one’s chest, suggesting that I marked it on a previous week’s transect.

If you’re looking for a northern grasshopper mouse, you are mostly likely to find them in sandy soils. They seem to prefer sandy areas that had sparser and often shorter vegetation. Apparently the sandhills portion of our Platte River Prairies are ideal habitat because they are loaded with northern grasshopper mice. It is exciting that we have such a robust population, especially because it gives us a chance to learn more about them.

The sandhills area of the Platte River Prairies - habitat of the northern grasshopper mouse. Can you spot the flag marking a trap location?

The sandhills portion of the Platte River Prairies – habitat of the northern grasshopper mouse.

Learning more about their habits will not only aid in our management of our prairie, but could potentially help fill some gaps in the broader scientific literature. While the life histories of some small mammals are pretty well understood, it seems to me that there is some updating to do in terms of the natural history descriptions of northern grasshopper mice. For example, most natural history sources will tell you that the northern grasshopper mouse is very territorial and will fight to the death any other grasshopper mouse that wander into its territory. However, Mike and I have been catching several northern grasshopper mice within 10-14 meters of each other. This seems like a much higher density than one would expect for a highly territorial species, especially one that is known to have a fairly large home range in relation to its size.

Greg Wright, a wildlife biologist at the Crane Trust says he’s seen reports that grasshopper mice might hunt as family units, which could explain the densities we were catching. [It will be intriguing to see if our data supports that idea]. It could also be that northern grasshopper mice are only especially territorial during the mating season? A small study in Colorado found that several individuals shared a burrow in the winter.

I think these critters have a compelling story, and I look forward to our future studies and new research questions so that we can expand our understanding of the awesome, fierce northern grasshopper mouse.

BEHIND THE SCENES

Can you spot Chris' black camera? You may think that Chris spends a lot of time wander through prairies flipping over leaves, but really, the majority of his photos are staged in a cardboard box... This is a behind-the-scenes look at the photo assistant setup during our first field day, when Mike and I brought a grasshopper mouse to show people before we released it. Can you spot Chris' black camera? You may think that Chris spends a lot of time wander through prairies flipping over leaves, but really, the majority of his photos are staged in a cardboard box... This is a behind-the-scenes look at the photo assistant setup during our first field day, when Mike and I brought a grasshopper mouse to show people before we released it.

Can you spot Chris’ black camera? You may think that Chris spends a lot of time wandering through prairies flipping over leaves, but really, the majority of his photos are staged in a cardboard box… This is a behind-the-scenes look at his photo setup during our first field day, when Mike and I brought a grasshopper mouse to show people before we released it.  The result was the first photo used in this post.

Editor’s Note:  Ok, two things, gigglepants.  First, have YOU ever tried to take a photo of a grasshopper mouse in the wild?  Exactly.  They don’t tend to sit still and pose, do they?   Second, I have not hidden my photo techniques in the past, and on the rare occasion when I use something like a cardboard box to get a photo that would be otherwise impossible, I try to be transparent about it.  Many readers will remember my very serious technical piece on how to use a wheelbarrow as a photo studio, for example.  At least I don’t use something silly like a plastic bag…  : )

Jasmine’s favorite s’mammal information sources:

University of Michigan’s Museum of Zoology Animal Diversity Web. This site has photos, skeletons/skulls, life history information, range, and usually some tidbits from recent studies.   http://animaldiversity.ummz.umich.edu/

Mammals of Kansas
Clearly, most of the range information is specific to Kansas. But has good pictures, good descriptions (lengths, weights, color), and succinct life history information.
http://kufs.ku.edu/libres/Mammals_of_Kansas/list.html.

The Colorado paper I mentioned:
Size and Habitat Characteristics of Home Ranges of Northern Grasshopper Mice (Onychomys Leucogaster). Paul Stapp. The Southwestern Naturalist, Vol. 44, No. 1 (Mar., 1999), pp. 101-105

Hubbard Fellowship Post – S’Mammals with Jasmine

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This is a post written by Jasmine Cutter, one of our 2014-15 Hubbard Fellows.  All photos are by Jasmine.

Howdy, Prairie Ecologist friends!
I remember how much I looked forward to the Fellows’ posts before coming to the Platte River Prairies, so I apologize for the glacial pace of my updates.  A considerable amount of my time and brainspace over the last two months has been occupied by small mammals (or s’mammals, as I prefer to call them). There are definite challenges to undertaking a project during the growing season (namely balancing project time and stewardship time), and throughout the process of the project and the summer there have been some unexpected surprises (mostly good), and a lot, a lot of learning.

Mike Schrad, Nebraska Master Naturalist and my small mammal project mentor.

Mike Schrad (left), Nebraska Master Naturalist and my small mammal project mentor.

In the briefest of terms, I’ve been tromping through our Derr sandhills (a unit which includes both restored and remnant prairie on the edge of the Platte River Valley), battling cows, thunderstorms, and a lack of sleep in the pursuit of learning more about the small mammal community in this unit. I was initially drawn to this site because the Derr sandhills contain pocket mice (Perognathus flavescens) and Northern grasshopper mice (Onychomys leucogaster). The pocket mice are minute, streamline and silky, whereas the grasshopper mice are beefy and aggressive (and probably also soft, but getting your finger near enough to find out is tricky), yet, despite their differences, they’re both endemic to sandy soils. As these critters are relatively unusual, my study will give us a chance to learn more about their habitat preferences, and hopefully enable us to manage the site in a way that ensures the continuation of healthy populations. Although these two species have remained the most endearing through out my study, my affection has also expanded to include shrews (they have venomous saliva and black-tipped teeth!), voles (ferocious teddy bears) and harvest mice (very agile and keep a neat nest). Deer mice tend to have a heavy parasite load and botfly sores (not to mention the possibility of hantavirus and carrying lyme disease), and therefore are often pretty icky. At this point, I am done with trapping for the most part. Soon, I will be collecting vegetation and site data for each trap site (that’s ~370 sampling points!), and this winter, I will be seeing if there are any relationships between the presence of certain species and site characteristics.

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Beefy lil grasshopper mouse, so-called due to their carnivorous diet. At night, they sing to defend their territories.

Pocket mouse. The clip on its tail is what is attached to the scale used to weigh them. While it is undoubtedly a little uncomfortable, there is no permanent damage. The clip is a helpful way to hold onto animals so I can take a photo. It’s essential to my study that I am able to document how the pelage (fur) color varies between individuals.

Pocket mouse. The clip on its tail is what is attached to the scale used to weigh them. While it is undoubtedly a little uncomfortable, there is no permanent damage. The clip is also a helpful way to hold onto animals so I can take a photo. It’s essential to my study that I am able to document how the pelage (fur) color varies between individuals.

Scary shrew teeth. Unlike the rest of the similarly-sized critters I caught, shrews are not rodents. They are in the order Soricomorpha. They are mostly carnivorous and have saliva that paralyzes their prey.

Scary shrew teeth. Unlike the rest of the similarly-sized critters I caught, shrews are not rodents. They are in the order Soricomorpha. They are mostly carnivorous and have saliva that paralyzes their prey.

There have been a few surprises during this project. For example, I have discovered that cows don’t like science. They have eaten my flags, licked my traps several feet off my transect, and squashed a few for good measure. If only their curiosity could be used more constructively!

One of the best surprises was opening one of my traps and finding a least weasel inside! I was waaayyy more intimidated by this critter than it was by me. Despite its ferocity, it was impressively lightweight. This littlest weasel was longer than the thirteen-lined ground squirrels that I also caught that day, but considerably lighter. The ground squirrels maxed out my 100 gram scale, whereas the weasel was only 70 grams! The weasel was also impressively smelly, living up to the family name of mustelidae.  I was a little worried that no other small mammals would go into that trap the next night because it smelled of predator, even after I sprayed it with Lysol. However, the harvest mouse I caught the next night was undeterred. No wonder s’mammals have such a short lifespan. Another surprising find on a different transect was an embarrassed-looking leopard frog. My bait seems to attract a lot of crickets, so I imagine that’s what lured the frog. And the cutest capture was these two baby voles that managed to wander into one trap.

Thirteen-lined ground squirrel (Ictidomys tridecemlineatus). When I open a trap, I gently plop the critter into a bag in order to minimize handling exposure. I can weigh, identify and sex the critter while it’s in the bag. It’s safer for me, and the animal is only in there for a few seconds to a minute.

Thirteen-lined ground squirrel (Ictidomys tridecemlineatus). When I open a trap, I gently plop the critter into a bag in order to minimize handling exposure. I can weigh, identify and sex the critter while it’s in the bag. It’s safer for me, and the animal is only in there for a few seconds to a minute.

Weasel tryptic. Although none of these manage to capture the full length of the weasel (Mustela nivalis), they do manage to capture what you’d be likely to see - a reddish blur.

Weasel tryptic. Although none of these manage to capture the full length of the weasel (Mustela nivalis), they do manage to capture what you’d be likely to see – a reddish blur.

Baby voles!

Baby voles!

In addition to the excitement of peeking into every closed trap, there have been other perks to the project. I’ve gotten to see way more sunrises and sunsets than I would have otherwise. I love the freshness of the mornings, how the grass glows orange, and the spiderwebs glisten, and how much my mood (and finger mobility) improves once the sun crests the sandhills. I’ve gotten to hear the weird robotic chirpings of the swallows at sunset. The light at these times is able to make pretty much any photo look amazing, so it’s a little less discouraging to compare some of my photos to Chris’. I have also really enjoyed the slower pace of sampling, of covering my transect by foot. I spend a lot of time in the prairies, but infrequently do I have time to slow down and appreciate how the prairie community changes meter by meter. I have gotten to know my transects well, and I look forward to seeing if/how the patterns I’ve noticed play out in the data.

I’ve taken thinking like a s’mammal maybe a little too much to heart. Whenever we visit a new prairie, I think, ‘this looks like good pocket mouse habitat, I wonder if they have any? I wish I had my traps…’. I am also really grateful that so many mammalogists have been willing to donate their time and resources. I’ve learned a lot about species identification from them, and it’s exciting to make new connections with other institutions.

Sunrise!

Sunrise!

My pile of science. Traps generously lent out by Montana State University and Kansas State.

My pile of science. Traps generously lent out by Montana State University and Kansas State.

Pocket mouse pockets. They store seeds in there to bring back to their nest cache.

Pocket mouse pockets. They use external fur-lined cheek pouches to store seeds until they can bring them back to their nest cache.

This is not to say that this project has not had its challenges. I would say the main struggles have been setting reasonable goals (never a strong suit), keeping track of all the moving pieces (Do I have all my equipment? Am I recording all the right info? When do these traps need to be mailed back to Montana?), not losing things (Luckily the two mice than ran off with my scale clips were recaptured the next day!), and figuring out how to do the majority of the sampling by myself. It has been a long, time-intensive process for just five sampling transects. And, the project has not been without its dangers. The most dangerous part of the study has definitely been cacti. You wouldn’t believe the number of cacti I’ve accidentally kneeled on, or kicked into myself! I don’t recommend it. But, when these aspects of fieldwork start to get me down, I remind myself that I caught a weasel, and that’s pretty freaking cool.