The Banner-tailed Kangaroo Rat: The Once – but probably not future – King

July 27, 2016 by

In 1977 when Jim Brown, Diane Davidson, and Jim Reichman started the Portal Project, the site looked like this:

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Photo of Portal Project from around 1977 (we think).

 

This desert heaven was home to a variety of small mammals. One of the most abundant of these was the Banner-tailed Kangaroo Rat. While I feel that most small mammals are adorable (*cough* *cough* Packrat), the Banner-tail is the one that is universally beloved by generations of Portal researchers.

 

summer 110

Banner-tailed Kangaroo Rat (Dipodomys spectabilis). How can we tell? Note its size relative to the hand and the white tuft at the end of the tail.

Kangaroo rats in general are lovely creatures. As their name suggests, these nocturnal rodents hop around like kangaroos on enlarged backlegs. As least one scientist has seen a kangaroo rat use those strong back legs to leap 5 feet horizontally (with a two foot ground clearance)1. They have a long tail which may play a role in locomotion1 and fur-lined cheek pouches that they use like a bag to carry around seeds they gather from the environment. Most kangaroo rats eat primarily seeds. A study in Nevada found that Merriam’s Kangaroo Rat (a species we have at Portal) has a diet of  approximately 70-100% seeds (it varies over the year) and they eat a small number of insects as well.2 Anyway, you get the idea, kangaroo rats in general are cool. Most kangaroo rats – like Merriam’s – are about 40-70 grams (that’s about 0.09-0.15 pounds). But there are a few kangaroo rats that are notably larger. The Banner-tailed Kangaroo Rat is one of these, being closer to ¼ of a pound.

 

So, in 1977 three kangaroo rats, alike in dignity in fair Portal where we lay our scene, coexisted without evidence of ancient grudge or new mutiny4: Banner-tails (Dipodomys spectabilis), Merriam’s (Dipodomys merriami) and Ord’s (Dipodomys ordii).

The plot below shows the population dynamics of the three kangaroo rats. The plot goes from 1977 to 20145 and shows the population size in energy use6. I like energy use – especially when I’m dealing with Banner-tails – because large animals need more food than small animals. So one large banner-tail needs the equivalent amount of energy as 2¾ Merriam’s (based on their metabolic rates). By converting the population numbers to energy use, it helps correct for this difference in food consumption. So, the graph shows that early on in the study, Banner-tails were energetically more dominant than Merriam’s or Ord’s.

Kangaroo_ratplot

This is data from our long-term site. Photo credits: Merriam’s by Sarah Supp, Ord’s by Andy Teucher via ZoocodeZoo.com, Banner-tail by an unknown Portal researcher (i.e. we forgot to document who)

This all changes, though in the mid 1980s. Why? Blame Tropical Storm Octave which dumped nearly half of the annual rainfall in less than a week7. While the other kangaroo rats barely noticed this event, the Banner-tails hated it. Many individuals disappeared over the following months. The population tried to stage a comeback in the late 80s and early 90s, but like a one-hit wonder band, it fizzled. By the late 90s, the era of the Banner-tail was over. The last Banner-tail disappeared and there was much sadness among the researchers.

But you’ll notice some blips. Like a heart that beats irregularly, every few years a few little lost souls, wandering across the desert, find our site. Hopes and dreams of a new era of banner-tails spring anew only to be crushed by disappointment when once again they disappear.

Why did the Banner-tails disappear after Tropical Storm Octave and why can’t they seem to make it at our site now? It’s not entirely clear, but we think it has to do with shrubs. Banner-tails love grasslands. They don’t mind a scattered shrub here or there, but they don’t like too many shrubs 8. Sadly, since 1977, the site has become steadily shrubbier. Below are paired photos taken from approximately the same location at the site. On the left is Jim Brown on plot 4 in the late 1970s. On the right is 19959. Notice any differences? The Banner-tails definitely do!

 

All of this is ancient history. So why blog about it now? Because we are happy to report the return of the Banner-tail! Well, kind of. I mean, we currently have one lonely female – probably fairly young given her weight and state of her fur when she showed up. We’ve caught her 3 months in a row now on plot 11. The students have joked about setting up a twitter feed for her. Tweets suggested include:

“4 months since I left home. The food here is great and all the other mice are small and easy to fight off. I’m gaining lots of weight”

“Returning to my favorite bed and breakfast this weekend. Predator-free and good but monotonous breakfast. Four out of five stars”

“Young professional female spectab [shortened form of the species name of Bannertails] seeking like-minded male. Looking for something casual and fun, no relationship. Interested suitors should arrive at Plot 11”

Needless to say, we’ve been excited by the Banner-tail. Every month we’ve been wondering “Is she still here?” One day, probably soon, the answer will be no because our site is too shrubby for a Banner-tail to be happy there, but for now we dream of fields of Banner-tails.

 

 

 

  1. George Bartholomew and Herbert H Caswell. 1951. Locomotion in Kangaroo Rats and its Adaptive Significance. Journal of Mammalogy. Vol 32. Pages 155-169.
  2. Glen Bradley and Roger A. Mauer. 1971. Reproduction and Food Habits of Merriam’s Kangaroo Rat, Dipodomys merriami. Vol 52 Pages 497-507.
  3. Ana Davidson and DC Lightfoot. 2008. Burrowing rodents increase landscape heterogeneity in a desert grassland. Journal of Arid Environments. Vol 72 pages 1133-1145.
  4. How Shakespeare should have written the opening to Romeo and Juliet. (Sorry, Shakespeare).
  5. I had this data on hand and was too lazy to update with the newest data
  6. How do we figure out energy use? We estimate it from metabolic rate. There is a well known relationship between the size of an individual and its metabolic rate – larger individuals have higher metabolic rates (i.e. they require more food per unit time than smaller organisms). We used an equation for the relationship between metabolic rate and weight that was calculated for wild rodents to figure out the metabolic rate for each individual and then summed across all individuals of the species.
  7. Thomas J. Valone, James H. Brown, Carrie L. Jacobi. 1995. Catastrophic decline of a desert rodent, Dipodomys spectabilis: insights from a long-term study. Journal of Mammalogy, vol 76, pages 428-436.
  8. Peter M. Waser and James M. Ayers. 2003. Microhabitat use and population decline in Banner-tailed Kangaroo Rats. Journal of Mammalogy vol 84. Pages 1031-1043.
  9. I keep meaning to take a recent version of this, but haven’t remembered to do this when I’m at the site.

PORTAL: The times, they are a’changin

July 14, 2016 by

Updates on temporal community dynamics, and a whole new project scheme.

PortalPano

Things have been quiet on the portal blog lately.

But in the lab and the field, it has been anything but.

 


Over the past year there have been big changes afoot for the Portal project.  In the summer of 2015, Weecology lab headquarters relocated from Utah State University in small, mountainous Logan to the massive University of Florida campus in subtropical Gainesville. So now we study Arizona’s desert rodents from the mossy groves of the southeast rather than the alpine forests of the Rockies, like true cosmopolitan, ever-curious ecologists.

GoogleMap

The Portal project headquarters relocated from Utah to Florida in summer 2015. Leaping Krat photo illustration by Molly Zisk, taken from http://www.ocregister.com

If you’re going to box up your life, you might as well reorganize it too. In the midst of planning her transcontinental move, Dr. Morgan Ernest, supported in her decision by funders at the National Science Foundation, decided it was time for a shuffle of Portal’s long-term experimental rodent community plots as well, a reorganization of the plot gates that allow some rodent species in, and keep others out. Yuri Kochiyama once said that movement is contagious. Barkpost.com said that science has finally proven that devoted dog owners often resemble their dogs. Maybe these things have nothing to do with the rigorous study of kangaroo rats in the Arizona desert. Maybe Yuri was talking about politics, not ecology and nobody actually thinks Peyton Manning looks like his dog. But maybe, when you study the ebb and flow of desert rodent populations for long enough, they have to move when you move. That’s not science. But stay tuned and we’ll tell you all about the real science of the Portal project plot move, and the people doing the moving. In the full words of Yuri, “the movement is contagious, and the people in it are the ones who pass on this spirit.”

YuriDogsActivist Yuri Kochiyama (Wikipedia.org) and people who look like their dogs (barkpost.com).
This is silliness.  Stay tuned for science.

It takes a community of people to shuffle a community of rodents, and to pass on the spirit of the Portal project.  To facilitate all this contagious movement, the Portal project lab group, like all strong biological populations, has grown in numbers over the past year. One might even call Dr. Ernest the Pied Piper of Ecology, enlisting a group of young followers in her slow migration from the mountains towards the sea. In 2015, she recruited another smammal (small mammal)-loving Portal RA, Ellen Bledsoe, to join Erica Christensen in conducting the monthly plot rodent census, officially appointed our own Glenda Yenni as Portal project manager, and brought in another graduate student, Joan Meiners, from Utah to help communicate the many exciting new projects radiating out of the Portal, Arizona site. And even though Morgan does know quite a lot about rats, we’re all pretty confident she’s not trying to drown us.

So now that we’ve gotten the debate about doppelgänger dogs, social activism, and old nursery rhymes out of the way, we can dive right in to the nitty gritty science of the new Portal project movement – what changes we made on site, and why.

Next time on this blog series, we’ll (re)begin our Portal project story in March of 2016, one year after the great plot shuffle of 2015, when this whole crew, plus two willing workers from Dr. Ethan White‘s side of Weecology, Shawn Taylor and Kristina Riemer, headed to the Arizona desert to check in on the plot switch, conduct the Portal project’s 447th rodent census and the 34th plant census (with a new high tech twist!), and dig a giant trench in a desert near-tornado.

PiedPiperThe Pied Piper, keeper of the rodent gates. http://www.mubi.com

Another Source for Portal Project Related Posts

April 16, 2015 by

We have plans to write about some cool things going on at Portal right now: changes in the treatments at the site, beautiful winter annuals, some changes in the rodent community. In the meantime, I thought I’d point people towards Pacifica Sommer’s blog. Pacifica is a PhD student at the University of Arizona who has been using camera traps to study rodents. She’s been coming out to the site regularly to set up camera traps on our plots to compare what her camera traps are seeing with what our live-traps are catching. Her videos are a real treat and we’ve been luck to have Pacifica coming out to the site. She occasionaly writes about her Portal adventures on her blog. Here are some of her Portal related posts:

I have heard the howling of the grasshopper mice

Footage of the Mighty Predator: Onychomys torridus

Energy, Temperature, and Sex

Energy and Sexual Activity

 

Monsoon Season

August 15, 2014 by

OLYMPUS DIGITAL CAMERA

Rainy season has arrived in Portal, AZ.  For those who are unfamiliar with the area, the majority of the year’s precipitation in the Chihuahuan Desert comes in July-August, also referred to as monsoon season.  Instead of the steady, prolonged rains that the word monsoon usually calls to mind, the Arizona version consists of relatively short but intense storms interspersed with periods of blue sky.  These storms also tend to be highly localized: you may watch the rain coming at you down the valley all morning, only to have it skirt around you to the west and miss you completely.  See http://www.wrh.noaa.gov/twc/monsoon/monsoon_NA.php for more information on the North American Monsoon. 

So far this year the Portal experimental site seems to be sustaining more hits than misses, and it’s shaping up to be a fairly “good” rainy season.  To see how the current season is measuring up to recent years, I’ve plotted total monthly precipitation through time in the figure below, with monsoon seasons highlighted as grey bands.  July 2014 was the 5th rainiest month in the past 14 years, exceeded only by the rainy seasons of 2004, 2006, 2008, and 2011.  And we still have August to look forward to! 

Time series of precipitation at Portal

Time series of precipitation at Portal

So what will this mean for our study?  One may predict that a pulse of precipitation in a moisture-poor ecosystem should cause an increase in plant growth.  Indeed, we have found evidence that the rainy season is correlated to a peak in vegetation, and that more precipitation generally means higher peaks. The following plot shows this (approximately) linear relationship between summer precipitation and summer vegetation.  The astute observer may notice that 2002 and 2007 managed to reach high levels of plant activity with low levels of precipitation.  I would first like to note that the site’s weather station was not operational during 2002 and so precipitation during this time was estimated using data from a nearby weather station which, due to the patchiness of storms mentioned above, may not be a valid estimation.  For 2007 I have no such excuse; either there are anomalies in the vegetation dataset I’m using (which is satellite-derived Normalized Difference Vegetation Index), or the rain-plant relationship is somewhat more complicated than I’ve assumed.  For the present season, if it keeps raining at the same rate we’ve seen so far, we will get about 180mm in total, putting my prediction of vegetation index at 0.42-0.43.  We’ll see how this pans out in another month or two. 

Precipitation vs. Vegetation linear regression

Precipitation vs. Vegetation linear regression

The response of the rodent community to rainy season is much more difficult to observe than the plant response.  The plant activity inspired by rainy season provides a surplus of food to the rodents, which encourages reproduction and should result in an increase in rodent abundance.  However, current research suggests that short-term weather events have little to do with rodent population dynamics, that models must incorporate weather patterns from the past year or more to detect subsequent changes in rodent abundance.  For example, numbers are not likely to increase after a single “good” summer monsoon, but they may if the site experiences a wet winter followed by a wet summer or two wet summers in a row. 

Researcher and researchee enduring inclement weather

Researcher and researchee enduring inclement weather

I want to conclude by thanking local contractor Bob Walton for the beautiful new roof on our ramada.  Just in time to keep our heads dry during this past sampling weekend! 

OLYMPUS DIGITAL CAMERA

Spring 2014 Plant Census

April 23, 2014 by

portal0314

Last month brought members of the weecology group (Dr. Morgan Ernest, recent graduates Dr. Glenda Yenni and Dr. Sarah Supp, and current graduate student Erica Christensen) back to Portal for the (approximately) semi-annual plant census.  Winter rains had provided us with a decent selection of annual plants to count and identify, which was a welcome contrast to the sparse plant census in spring 2013.  The breakout stars this year were smallflowered milkvetch (Astragalus nuttallianus), which showed up hundreds-strong in some quadrats, Esteve’s pincushion (Chaenactis stevioides), and the invasive redstem stork’s bill (Erodium cicutarium).  One of the most striking desert flowers found in the area, the California poppy (Eschscholzia  californica Mexicana), was also present on many plots.

Eschscholzia  californica Mexicana

Eschscholzia californica Mexicana

In total, we identified 28 annual plant species, a marked improvement from the 16 species recorded in the spring census of 2013 and quite similar to the 30 species recorded in 2012.  However while species composition was similar in years 2012 and 2014, plant abundances were much lower in 2014.  This is likely due in part to differences in total winter precipitation; precipitation was high in 2012, very low in 2013, and somewhere in the middle in 2014.

Abundances of the top 10 species for the past 3 years: Astragalus nuttallianus, Erodium cicutarium, Chaenactis stevioides, Lesquerella gordoni, Descurainia pinnata, Phacelia arizonica, Linanthus bigelovii, Eschscholzia californica mexicana, Eriastrum diffusum, Lepidium lasiocarpum

Abundances of the top 10 species for the past 3 years: Astragalus nuttallianus, Erodium cicutarium, Chaenactis stevioides, Lesquerella gordoni, Descurainia pinnata, Phacelia arizonica, Linanthus bigelovii, Eschscholzia californica mexicana, Eriastrum diffusum, Lepidium lasiocarpum

We also used the trip to perform some much-needed maintenance on the site.  The low fences around each of our 24 experimental plots require frequent upkeep to prevent the rodents from tunneling under or climbing over them, but there is also a barbed wire cattle fence around the perimeter of the 20 ha site that has gotten very little care in the past decade or so.  It only came to my attention in March, when I was surprised to find a very large herbivore chewing his cud on my study site.  We were able to chase him off with minimal damage (either physical or emotional) to man and beast, but the experience inspired me to request the help of my PhD adviser in repairing some conspicuous holes in the perimeter fence.  So how many PhDs does it take to mend a barbed wire fence?  Turns out one and a half will get it done.

Dr. Morgan Ernest deftly handling some baling wire for fence repair

Dr. Morgan Ernest deftly handling some baling wire for fence repair

The cow wasn’t the only unexpected herbivore we encountered during the March rodent census.  Caught in one of the traps, seen for the first time on the site since 2009, was a tawny-bellied cotton rat (Sigmodon fulviventer).  Three species of cotton rat have been recorded at the site (S. fulviventer, S. hispidus, and S. ochrognathus), all of which prefer grass-dominated habitat to shrub-dominated.  They have been uncommon but persistent at Portal since its inception in 1977, and were even fairly abundant when the area was dominated by lush grasses in the mid to late 2000s.  However recent years have seen decreased rainfall and therefore the plots have been more characteristic of shrubland than grassland, and the Sigmodons moved elsewhere.  Does the return of the cotton rat mean a return to grassland is on the horizon?

S. fulviventer wasn't as excited to see me as I was to see him

S. fulviventer wasn’t as excited to see me as I was to see him

The Portal Project Phase 2: Coming Soon

March 18, 2014 by
Winter annuals from 2012(?). Beautiful blooms like this seem to be an increasingly rare sight!

Winter annuals from 2012(?). Beautiful blooms like this seem to be an increasingly rare sight!

Stay tuned. The Portal Project blog is coming back on line with new material and new contributors! We’ve been busy at the site with some cool results and a new grant to fund new directions. We’ll start posting about it all soon. For those of you who follow this blog, previous contributors Sarah Supp and Glenda Yenni have both graduated, though they are both still working on Portal projects and come back to the site from time to time! Erica Christensen has taken their place and plans to post regularly about what’s going on at the site. In the meantime, let this beautiful picture by Glenda in the Portal archives suffice until we finish writing up some new material for the blog!

 

What’s going on outside the Portal site?

December 7, 2012 by

The 20-hectare Portal research site has been studied for over 30 years now – and we’re still learning new things! But every additional year brings up new insights and new questions about the ecology happening in that patch of the desert. Why did certain species disappear? Where did new species come from? How important are changes in the weather to the persistence of species? Are there important trade-offs in rodent survival strategy (i.e., competition vs. dispersal)? How important are plant dynamics to rodent species composition (or vice versa)? What might we be missing by only focusing on rodents and plants?

Image

The Portal research site, and fencing around a rodent trapping plot.

One major question we’ve been thinking about more lately is the connection of the 20-hectares patch of desert that we study (Portal) to the surrounding desert. Since we know that rodents species come and go throughout the years, and they must be coming and going to somewhere else, we decided to venture outside our usual trapping grids for a few days to see what’s going on outside the Portal site.

October 12-17, a subset of the Ernest and White labs (Morgan, Glenda, Ken, Erica, and myself) travelled to do the usual monthly rodent-trapping and to trap 12 additional “outside” areas within walking distance of the site. We tried to trap in areas that might have different characteristics, because locations with different vegetation or topography could support different rodent species than we might expect at the Portal site. Our sites included two cattle tanks, some arroyos, areas grazed by cattle, and an area that used to be a study site for Peter Waser (he studies banner-tailed kangaroo rats), and has been cleared of shrubs.

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Cattle tanks collect rainwater, but are actually dry most of the year. This one looked like a mini-grassland.

To learn about the rodents that might occur outside of Portal, in each site we set a rodent trapping grid approximately the same size as a Portal plot (50 meters x 50 meters) and sampled the vegetation by counting the plants along an X-shaped transect. We marked our rodent trap location with pink flagging tape, which was a great idea, because otherwise it would have taken *forever* to find and pick up our traps the following morning. It turns out that walking in a straight line in the desert without a guide is really hard!Image

 

The portal crew setting out rodent traps. See the pink flagging?

We didn’t do our usual plant-survey at Portal this fall, and mid-October is a bit late in the season, but we were able to confidently identify most of what we saw, even if the plant was already going to seed. Most of the crew was new to plant transect work, but I think they were convinced that counting plants isn’t that bad, at least until we came to our final riparian area, which was full of catclaw acacia (Acacia greggii). “Cat-claw” acacia is as horrible as it sounds… like thousands of tiny, angry kittens clawing at your clothes, face, and hands. Except that these angry kittens leave the tips of their claws in your skin. Yes, we left with plenty of battle scars!

Image

The white line down the center of the photo is the transect tape for our vegetation survey. The green stuff is a thicket of cat claw acacia. Worst. Transect. Ever.

Overall, the trip was a success, and I think that everyone had a good time. Research is exciting and fun when it’s done right! I left wishing we could spend more time exploring the desert around Portal and learning more about the natural environmental gradients that might be an important part of what’s driving observations at our site. So many ecological studies are done at small spatial and temporal scales, but understanding species dynamics and connectance across a landscape is an important challenge for ecologists. Hopefully, our mini-exploration was just a first step in beginning to understand our research in the larger context of the Chihuahuan desert landscape.

September Portal update

September 30, 2012 by

In September, I returned to Portal bringing with me the newest Ernest lab member, Erica Christensen. It was a bit cooler than usual for mid-September, but overall, a great time of year to be in the desert. We captured 263 rodents, most of which are still represented by the desert pocket mouse (Chaetodipus penicillatus) and Merriam’s kangaroo rat (Dipodomys merriami). It’s much less buggy than other years, and it was a really pleasant weekend. No complaints about desert fieldwork in the fall!

dipodomys merriami

Merriam’s kangaroo rat.

pocket krat

A small kangaroo rat warms up in my pocket before being released. Sometimes after a cool night, rodents need a little help in the morning.

EricaCandPE

Erica helps process a cactus mouse (Peromyscus eremicus).

jumping Spider

We found this guy, jumping spider Phidippus octopunctatus, on a shrub while exploring the area surrounding the site.

zinnia grandiflora

We didn’t conduct a formal plant survey this fall due to logistical constraints, but many flowers were blooming in September. Here is a small perennial, Zinnia grandiflora.

Coatis and programmers in the desert

September 25, 2012 by

An update from the May Portal trip (which occurred immediately after my Giant Kangaroo Rat foray):

Recent USU graduate, Ben Morris, who had been working with the Weecology lab for the past few years, finally made it out to our field site, just before starting his Ph.D. with the Hurlbert lab at UNC! Ben spends most of his time on the computer being a ninja at utilizing ecoinformatics and big data, but he proved quite worthy in the field. We also saw a coati in the middle of the desert. Not sure what it was doing out there, but it didn’t look too happy… (sorry, no coati pictures to prove it!)

Ben and onychomys

Ben weighs a grasshopper mouse.

Ben measures the hind foot length of a kangaroo rat.

Portal Squee: Nesting Cactus Mice

September 25, 2012 by

This post is way overdue, but the photos are so cute that I couldn’t help myself. Back in March 2012, when Glenda Yenni, Xiao Xiao and I travelled to Portal to count the winter plants, we discovered cactus mice (Peromyscus eremicus) nesting in a box that we were using to hold firewood. When we took the wood out of the box, there was a flurry of activity and a big fluffy nest inside!

Peromyscus eremicus in a box

A scared cactus mouse runs around the box.

What was even more interesting was that the nest had a two (eartagged!) adults  pair with 2 different ages of offspring! There were 3-4 subadult mice along with 2-4 teeny tiny juveniles (it was hard to count in the dark with all the running around). The juveniles were small enough (although they did have hair) that they remained attached to the nesting female when she ran out of the nest.

I mentioned this to Karen Mabry, who sometimes helps out at Portal, and she suggested that although not much seems to be known about Peromyscus eremicus, they may be “more monagamous” than some other species mice. Some other Peromyscus species are known to be socially and genetically monogamous, and have sometimes been confirmed as nesting with sisters (rather than a male-female pair), which could potentially explain why there were 2 different ages of juveniles in the nest box.

Peromyscus eremicus in nest

Female cactus mouse peers out of nest.

(Photo credits: Glenda Yenni)


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