Tag Archives: plains pocket mouse

Hubbard Fellowship Blog – Plains Pocket Mouse

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This post is written by Jasmine Cutter, one of our Hubbard Fellows.  She has been studying the way small mammals use our restored and remnant prairies.

Remember when I said I was going to highlight some more of our small mammal species? Well, at long last, here’s the second installment!

The plains pocket mouse.

The plains pocket mouse (Perognathus flavescens).  So Cute!  Notice the small eyes, small ears, and white dot under the ear.  Top tends to be brown/buff-colored, with a yellowish line along its side and a white underbelly.  Photo by Chris Helzer

Arguably the sleekest and most adorable of the critters I caught, the most distinguishing feature of the plains pocket mouse (Perognathus flavescens) is its fur-lined cheek pouches. Fur-lined cheek pouches!!! Imagine if, when you opened your mouth, on each side there was a little fur-lined pouch that ran all the way back to almost your shoulders! Gives me the heebie jeebies to think about, but pretty awesome if you’re a pocket mouse. The diet of the plains pocket mice is almost entirely grass and weed seeds, and the pouches allow them to carry seeds back to their burrows and cache them.

Based on what I read, it’s thought that the purpose of these pouches being fur-lined is to conserve spit. Pocket mice and their relatives (other pocket mice, kangaroo rats, kangaroo mice) are often associated with arid environments and these critters are all extremely water efficient. The thought is that if pocket mice had a hamster-like pouch, then every time they spit out the seeds they were carrying they’d be wasting precious moisture. If the pouches are fur-lined, then no spit wasted!

fur-lined pockets

Look at those cheek pouches!  Remember, I was only holding this critter for a few seconds before I released it.  only a temporary undignified moment, and then back to the sandhills!

These adaptations help the plains pocket mice go for six weeks without water! Most of the moisture they need is obtained from seeds and their kidneys are extremely efficient. Furthermore, their habits also lend to water conservation; pocket mice spend most of the day underground in burrows where it’s cooler and more humid, they plug their entrance holes to keep in moisture (and keep out predators), and they can change slow their metabolism (enter torpor) when it’s too hot or too cold.

The other crazy thing about the plains pocket mouse is that it is not closely related to any of the other rodents* that I caught. Those other rodents  — northern grasshopper mouse, deer mouse, harvest mouse, voles — all belong to one taxonomic family Cricetidae (which includes true hamsters, voles, lemmings and New World rats and mice), whereas the plains pocket mouse is from the family Heteromyidae. Heteromyidae includes kangaroo rats, kangaroo mice, and pocket mice, though none are technically rats or mice. In fact, the plains pocket mouse is more closely related to pocket gophers than to any other rodent I caught!

This is a very simplified phylogenetic tree of the Order Rodentia. Phylogenetic trees show the inferred evolutionary relationships among species based on similarities/differences in physical and/or genetic characteristics. So whenever two branches come together, it's understood that the join represents the most recent common ancestor. FYI, there are a lot of other critters in the Order Rodentia that are not shown; there are 5 suborders I'm not showing and many branches that diverge from those suborders. Also length of lines is for convenience and doesn't represent any timescale.

This is a very simplified phylogenetic tree of the Order Rodentia. Phylogenetic trees show the inferred evolutionary relationships among species based on similarities/differences in physical and/or genetic characteristics. So whenever two branches come together, it’s understood that the join represents the most recent common ancestor. FYI, there are a lot of other critters in the Order Rodentia that are not shown; there are 5 suborders I’m not showing and many branches that diverge from those suborders. Also length of lines is for convenience and doesn’t represent any timescale.

All this is very interesting, but doesn’t help you identify a plains pocket mouse if you saw it in the field… In my mind, its key identifying features include its small size (usually 7-15 grams, 99-150mm nose to tail tip), small ears usually with a white dot below them, grooved upper incisors (if you hold them by their scruff, you’ll see a line down each upper incisor), and of course, their cheek pouches! They tend to be dark on their back, with a yellowish (“buff-colored”) line on their sides and white/pale underneath.

They are most frequently found in (usually sandy) areas with friable soil. Sandhills are a good bet, as are other fields that have open sandy patches, especially ones that are grazed so they’re more open. In general, plains pocket mice seem to prefer sparsely vegetated areas (hopefully my data will test whether that holds up on our properties).

The author collecting vegetation data for her small mammal research project.

The author collecting vegetation data for her small mammal research project.  Photo by Chris Helzer

In terms of why we care about them, well, they have awesome cheek pouches and barely need any water!!! What else do you want?? Just kidding, there are many more reasons why it’s worth paying attention to them. Most importantly, we still don’t know that much about them. Not a lot is known about their mating or winter habits, and until recently there were sizable gaps in our understanding of their distribution in Nebraska (see Geluso and Wright 2012).

The plains pocket mouse can be found throughout the Great Plains – from Northern Mexico to Minnesota and the Dakotas; yet, it’s local distributions are less well understood. There also seem to be noticeable differences between critters on the western end of their range and the eastern end. So much so, that there are two recognized subspecies of the plains pocket mouse. There is a western subspecies, P. f. flavescens and an eastern subspecies, P. f. perniger.** The eastern subspecies is considered rarer and has been deemed a Tier 1 At-Risk species by the Nebraska Game and Parks Natural Legacy Program.

Look! A photo of me taking a photo of a pocket mouse!

A photo of me taking a photo of a pocket mouse!

Our Platte River Prairies are right at the edge of the alleged dividing line between the range of the western subspecies and the range of the eastern subspecies, which makes it an especially interesting place to study them. Are we seeing the eastern subspecies, or the western? At this point, the answer seems to be “yes!” Hopefully our population(s) will help the experts to parse the differences between the two subspecies and their range. Trying to define ranges is always tricky, especially because sometimes it’s hard to tell whether a species is actually not in a place, or if people just haven’t looked for it there.

All of this is to say that there’s a lot more work to do! It’s exciting to study a critter that is still fairly enigmatic, and I’m excited to see what future studies discover both in terms of life history knowledge and range/subspecies questions!

* Rodents are from the Order Rodentia, i.e., all the critters I caught except the shrews, the weasel, and the frog.

** The differences between the subspecies are very nuanced and my previous description (and pictures!) should still allow you to identify them as a plains pocket mouse.

Realistic Motion Photography (Of Cute Fuzzy Mice)

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You may remember a previous post in which I described a project to evaluate the impact of our prairie restoration work on small mammals.  Mike Schrad, a Nebraska Master Naturalist, is helping us collect some pilot data to see whether small mammal species in our remnant prairies are also using the adjacent restored prairies.  Mike is now in his second season of that project, and last week he had a great start to this collecting season.  Among other species, he caught a number of grasshopper mice and plains pocket mice in some upland sandy areas of our Platte River Prairies.

There will be more to come on those mouse species and the significance of finding them (especially the plains pocket mouse, which is a Tier 1 species (high conservation priority) in the Nebraska Natural Legacy Plan).  Today, though, I wanted to share some distinctive photographs of the two species.  I hope it will be immediately clear that I’m experimenting with an exciting new style of wildlife photography – one that represents a more realistic view of how people generally see wildlife.

This might be my favorite photograph of the batch. Note how easily you can see the smudge of light-colored fur beneath the blurry ear, and the indistinct yellowish streak along the body. Along with size, those are the distinctive characters that best separate these pocket mice from other species.

This might be my favorite photograph of the batch. Note how easily you can see the smudge of light-colored fur beneath the blurry ear, and the indistinct yellowish streak along the body. Along with size, those are the characters that best separate pocket mice from other species.

After getting a couple of dry and boring documentary photos of a plains pocket mouse in Mike’s hand, we put one into a cardboard box in order to get something a little different.  It worked so well, we repeated the process with a grasshopper mouse.  I’m sure you’ll agree that these photographs portray these little creatures as we typically see them in the wild, unlike many of the photos you see in so-called “wildlife magazines” and “nature websites”.   Those tack-sharp photographs of animals sitting perfectly still and displaying their most charismatic features and poses in beautiful light are completely unrealistic.  Who wants to look at them?  Exactly.  What’s much more useful are photographs that show these creatures just as you might see them while hiking – a quick blur of fur zipping from one bit of cover to the next.

Here's a great shot of the long blurry tail pocket mice are known for. Note how pink it is as it streaks past...

Here’s a great shot of the long blurry tail pocket mice are known for. Note how pink it is as it streaks past…

Here's an even better shot of the tail, without any of the distractions of the mouse's body itself. This is how I often see mice in the field (except for the cardboard box, of course).

Here’s an even better shot of the tail, without any of the distractions of the mouse’s body itself. This is how I often see mice in the field (except for the cardboard box, of course).

When we put the grasshopper mouse in the box, I experimented with providing a more natural background of dried grasses. I'm not sure yet if I like the effect. It almost seems like it distracts from the subject...

When we put the grasshopper mouse in the box, I experimented with providing a more natural background of dried grasses. I’m not sure yet if I like the effect. It almost seems like it distracts from the subject…

Note the larger size, fuzzier (and shorter) tail, and grayer fur of this grasshopper mouse as it streaks past.

Note the larger size, fuzzier (and shorter) tail, and grayer fur of this grasshopper mouse as it zips past.

This one came out almost too sharp to be useful, but it does show the pointy nose that helps distinguish the grasshopper mice from other species.

This image highlights the pointy nose that helps distinguish the grasshopper mice from other species.

Some people will probably see these photos and think I’m just concocting wild justifications to cover my inability to take good sharp photographs of these little mice.  Those people obviously have no imagination or appreciation for the field of realistic motion photography, which I am currently developing and describing.  They will probably also not be among those who flock to buy my forthcoming field guide to wildflowers, entitled “Roadside Wildflowers at 60 Miles Per Hour”, in which each wildflower species is represented by a blurry streak of color that shows how it actually looks as you drive by on the highway.  I feel sorry for those people.

On the other hand, to you readers who appreciate my pioneering work, thank you for your support, and I hope that you’ve enjoyed my first attempt in this new medium.  Be assured that I’ll take many more similar photographs in the future, and will probably share some of the blurriest – and thus most useful – with you.