ALL GOOD THINGS MUST END, OR SHIFT

August 3, 2016 by

We return this week from our special, breaking-news post about the recent reappearance of our one-hit-wonder, Twitter-sensation, spectabulous Banner-tailed Kangaroo Rat. This T-Rex of Portal may not be here to stay, but we’re sure excited she stopped by. What is here to stay is that pesky plot switch we mentioned last month. We’re going to continue our series of Portal science updates and tell you all about that now:


REGIME SHIFTS AND A NEW FRONTIER AT PORTAL

The last time we checked in at this blog prior to the 2015 plot switch, Erica was battling monsoon season to record desert rodent dynamics on the twenty-four long-term experimental plots that have been censused almost monthly since the site was established in 1977 by James Brown, James Reichman, and Diane Davidson. That’s thirty-nine years of tracking the occurrence of various species of small mammals. That’s over four hundred visits to Portal, AZ to trap, measure, weigh, and tag rats. And it all started before scientists had thought very much about why fluctuating species abundances in a community might be interesting.

This is cool because now we have decades of data (most of it publicly available) on how these scurrying, hopping, burrowing creatures have been interacting at Portal, just in time to see a surge of researcher interest in community ecology and species dynamics. For example, we were able to document an abundance of the small, pink flower Erodium cicutarium in plots where the competitive seed-foraging Kangaroo rats were excluded (Allington et al, 2013). And, after many years of pondering its absence, we recorded a resurgence of the Northern pygmy mouse, Baiomys taylori, a peculiar trend that would have gone undetected without regular sampling efforts. We’ve seen shrubs increase in both size and abundance, changing the entire look of those plots, not to mention the nature of the local foraging and shade resources. Ecology, in all its complexities, happens over long time scales. To understand it, we must record it over short ones. Few studies exist that have managed to do both, and we are excited about the scientific opportunities the history at Portal affords us and others who use our data.

Erodium cicutarium (left) has been increasing in abundance in plots where Kangaroo rats are excluded.  Baiomys taylori (right), the Northern pygmy mouse, has resurged from apparent rarity.

So now that we have amassed this monstrous dataset and finally understand more about how these rodents have been faring, cohabiting, and influencing the plants of these twenty-four plots in long-term treatment groups over nearly forty years, naturally we decided to turn it all on its head. Yes, after over four hundred samples of the twenty-four plots in their original treatment states, we got a grant from the National Science Foundation to switch them all around. Why? Because we’re scientists, and we like to poke systems to see what happens.

Because we scientists often want to be useful in addition to curious, we also like to simulate real expected ecological change so that we can predict likely outcomes and plan for them. Our world is rapidly changing. We need to understand how ecological communities will respond. When we’re not watching and recording, or sometimes even when we are, seemingly small changes can add up to big shifts. A breeze, a little water vapor, a small temperature change can suddenly turn into a monstrous hurricane, for example, that introduces a whole new set of rules and challenges to human existence.  Similarly, ecological systems can undergo extreme, abrupt changes in state that are very hard to understand and manage unless they have been tracked before, during, and after that transformation.

Questions surrounding the idea of regime shifts, described as dramatic changes in populations, communities, and ecosystems over short periods of time (Hare & Mantua, 2000), represent relatively new challenges in the field of ecology, ones that the Portal project may be uniquely situated to address.  Understanding regime shifts, or how communities of rodents may suddenly shift in their relative species abundances or resource usage, at Portal may help us understand what to expect from other ecosystems undergoing unprecedented levels of environmental change.  We’re not promising X-(woman)-like vanquishing of Hurricanes. We study rats, not wolverines after all. But this is important stuff.

Hurricane

While hurricanes are exceedingly rare in the Arizona desert, there are subtler forces at work which may cause shifts in our Portal rodent community. Knowledge of these forces may help us, and other scientists, understand similar sudden disruptions in unmonitored groups and ecosystems. It’s the scientists’ mutant superpower — studying one thing ‘over here’ can help us predict and manage another thing ‘over there’ which we may have actually never seen…except in our mind’s eye.

The figure below, from Dr. Ernest’s 2014 grant proposal, shows three scenarios in which ecosystems and drivers (e.g. climate, nutrient input, biotic interactions) can be related in ways that might represent system-disrupting regime shifts. Sudden shifts in drivers (e.g. hurricanes) could cause a corresponding shift in ecosystems (e.g. massive urban destruction), which would constitute a regime shift. The same ecosystem pattern, however, could be triggered by simply crossing a threshold along some seemingly innocuous linear increase of a driver (like a slowly rising sea level that causes the sudden collapse of a city when it finally submerges the business district, or the state of water as it’s gradually heated past its boiling point). Regime shifts, like the melting of sea ice caps, can be hard to undo. Sometimes an ecosystem can be brought back down from a boil by turning down the driver dial. But sometimes an ecosystem will fail to revert back to its original state after a driver has increased and then decreased again, taking the ecosystem along a new trajectory. At Portal, where neither massive urban destruction nor hurricanes are a major concern, this might come in the form a plant that fails to return to a location after a particularly dry summer even after rains have resumed, or a Banner-tail Kangaroo rat who once reigned mighty and may never be seen again.

Fig1


To poke the system and test this at Portal, in March 2015, we reversed some of the long-standing plot treatments. We also, of course, maintained some of the plots in their original treatments to serve as reference plots, against which we can test the existence and magnitude of potential regime shifts caused by introducing a large granivore as a driver. This has rarely been experimentally tested because few systems have the long-term data, ability to simultaneously cause a jump in an ecosystem driver in both directions, and enough plots to maintain replicates with reversed and reference plots.

Fig2

The Portal project’s twenty-four plots and well-monitored, gated rodent communities is an ideal system to study regime shifts because it does not have these common experimental design limitations. Because we manipulate rodent access to plots via gates of different size, it is also shockingly easy to change the rodent community on a plot – we can make new gates by clipping holes in the fencing, remove gates by applying patches over them, or change the size of gates (and the species that can enter the plot) by either patching or clipping to create new hole sizes. So last spring, Dr. Morgan Ernest led the hardware-cloth-stripping-team in reassigning plots to their new experimental treatment, ending an era, but never the science:

Erica securing the new hardware cloth pieces to close the old gates (left).  This little guy (right) wishes we could strip the hardware cloth off him.  But we are done with that task.

In a gesture of inclusiveness and diversity characteristic of the Weecology lab group ideology, we broke down barriers between different rodent communities by enlarging or creating gates in some of the plots that had previously excluded the granivorous, large-skulled (and adorable) Kangaroo rats:

KRat

A Kangaroo rat, Dipodomys merriami.  What plot wouldn’t want these cuties?

But because this is science and not social revolution after all, we are also testing the influence of these large-skulled favorites as ecosystem drivers by excluding Kangaroo rats from some of their previous home plots by patching up or narrowing gates in plot fences that had previously allowed them to pass into these areas.

Example of a gate in a Control plot, open (left) and closed (right), which provides free, open access for all knowledge-(or seed)-seeking rodents!
Example of a gate in a Kangaroo rat exclosure plot, open (left) and closed (right), which is very oppressive of Krats, but great for controlling their influence in plots as a driver.

 

In case you have ever doubted the dedication of field biologists, thinking perhaps that we enjoy a life of sipping Coronas in a scenic field station after a day of wandering through the hills sniffing at plants, we would like to explain to you the unnatural nature of hardware cloth. Hardware cloth is not cloth. It is, however, hard. It is also pointy and sharp and vexingly narrow. To enact the plot treatments switch described above, the valiant hardware-cloth-team-of-2015 used pliers to strip countless thin layers of wire off of small metal squares of fencing, creating exposed, pointy wire ends along the hardware cloth, which must then be woven through the tiny squares in the existing plot fence to close off or narrow old treatment gates. They then cut or adjusted new treatment gates in the existing fence hardware cloth to create new access for the Kangaroo rat ‘drivers.’ Science is not all high-tech gadgets and sophisticated computer algorithms. Sometimes real science is stabbing yourself with hardware cloth one thousand times and squatting on the ground in the blazing hot desert to sew patches over gates in metal fences because you want to see what the rats will do. We happen to actually love this type of self-brutality in the name of science, and how it makes our evening Coronas, enjoyed together around the campfire at our beautiful field station, taste that much better.

Ramada

The field crew taking a break at the Ramada, our two-sided field station.

And that is the story of how the plot switch, and the finger-massacre, of 2015 was recorded in Portal history. We won’t show you the blood, but we will show you the final plot map result, and a much cleaner schematic of plot treatment shifts:

Fig3

Fig4

 

Next time on the Portal blog we will fast-forward to a year after this historic plot switch when, wiser, hardier, and with more Band-Aids and guacamole in tow (though there is never, ever enough guacamole), the Weecology field crew hit the road again, in our new University of Florida vehicle, to undertake the 447th sampling of desert rodents, and the twelfth under a possible new regime.

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:

image018

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.

Image

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.


Follow

Get every new post delivered to your Inbox.

Join 1,628 other followers