Holiday season with the Portal rats

Trapping at Portal is usually done on the weekend closest to the new moon. This is done for a number of reasons: 1) trapping at the same time each month lends consistency to our methods, and 2) evidence suggests that rodent may be most active outside of the nest under the cover of the darkest time of the month (but then again, maybe not). This year, the new moon fell on the day after Thanksgiving and again on Christmas Eve. As much as I enjoy handling rodents, I pushed back the monthly Portal trips to the first (Dec 2-4) and third quarter (Dec 16-18) of the lunar calendar.

When the temperatures drop, many of our smaller species disappear for the winter as they enter torpor to save energy and remain warm in their burrows. Although larger species, such as the kangaroo rats and grasshopper mice stay active year round, they are still susceptible to cold desert nights, which commonly dip as low as 20 F in the winter! Getting wet, even a little bit, when it is so cold can kill even these larger individuals. So when I arrived in Arizona on Dec. 2nd to see rain clouds in the sky,  I knew that trapping that weekend was just not going to happen.

Given the total lack of rain last winter in southeastern Arizona, and the nasty fire season they experienced this past summer, the rain is much needed. So although we weren’t able to set out traps, Tim Bean, visiting from UC Berkeley (where he studies the endangered giant kangaroo rat!), helped me with some site maintenance activities.

Erosion around the gates in our fences has continued as the rain falls, so we took advantage of the damp soil to rebuild little ‘ramps’ for the rodents to use to ensure that immigration and emigration from fenced plots can still happen.

While walking around all the plots, we also filled in holes that seemed to go under our fences. Here, a badger has successfully created a superhighway into one of our total rodent exclosure plots, right under the bottom of the buried wire mesh.

Here, Tim valiantly fills in the hole. Not a very good substitute for getting to see cute kangaroo rats, but it had to make do.

Germination has already begun, and if the rain keeps up, there should be a lot of vegetation this spring!

For the second December trip, I brought along ASU researcher with the CAP LTER, Julie Ripplinger, and we were lucky enough to be able to set traps one night, despite rain clouds lurking in the sky.

Julie is pictured here holding a cactus mouse (Peromyscus eremicus), which seem to be relatively abundant right now! We caught nearly all of them in pairs, one trap right next to the other and nearly all were in breeding condition. Cactus mice may breed year-round if conditions are right. They are also quite pretty mice with their orange-y sides, large ears, and very soft fur.

In addition, we continue to catch a solitary Bailey’s pocket mouse (Chaetodipus bailey); the species that was once our most dominant seems to be hanging around nearby…

Rain clouds hung around all day on Saturday (Dec 17) so we erred on the side of safety and didn’t set traps on our final night. Instead we completed more plot maintenance, this time focusing on stabilizing our trap shed. The shed is one of those snap-together plastic outdoor sheds which works fine for our purposes, but from time to time begins to fall apart and needs snapped back together. During the past two weeks, something dug a large hole underneath so it was completely destabilized. I wanted to take it completely off its cobbled-together rock base and rebuild it, but Julie stopped me when she saw the tail of a mojave rattlesnake poking from underneath the shed near my hand. Again deciding to err on the side of safety (snakes often overwinter in large groups, called a hibernaculum), I satisfied myself with carefully filling in the part of the hole I could see and stabilizing the roof of the shed.

 

October Rodent Census

October is one of my favorite months to be at Portal. The day and night temperatures seem perfect and the days are long enough to enjoy the scenery of the desert. Because of this, it’s also one of the best times to introduce new Portal volunteers to the site. Throughout the project’s duration, many people have come to help with the rodent and plant censuses, and many of these people have not been graduate students or even biologists. This month, I was able to bring my mom, Mary Mohlman, who works at Lincoln Elementary School in Hastings, NE. Her students have actually been studying deserts this fall, so she was excited to learn about the rodents and to take lots of pictures to show the kids.

Mary helping to set traps in the late afternoon.

Mary Mohlman getting to know a desert pocket mouse which was trapped on a total rodent exclosure plot. These individuals are set free off-site after being identified and measured.

Rodents are fun!

Our trap numbers continued to increase and we had nearly 200 individuals! In addition, some of our other species made a few cameos, including four cactus mice (Peromyscus eremicus), 4 southern grasshopper mice (Onychomys torridus), 2 silky pocket mice (Perognathus flavus), and even a new Bailey’s pocket mouse (Chaetodipus bailey)! We had one strange encounter with a very, very pregnant female kangaroo rat (Dipodomys merriami) who weighed over 60 grams (usually ~ 35-45 grams)! As soon as we let her go, she started making urgent squeaking noises and ran about 5 feet away from us towards the corner of the plot where she dug a hole, climbed inside, and covered the entrance. For the next 10 minutes, as we finished the rest of the traps on the plot, we could hear her squeaking while underground. I can’t say what was happening, but it was very strange behavior.

A new Bailey's pocket mouse. So far, its still the only one we've caught on the site in the last few months.

The rain seems to have stopped for the season and the vegetation was much drier than a few weeks ago when we completed the plant census. However, there were still plenty of very large centipedes (Scolopendra spp.) and texas horned lizards to be seen (Phrynosoma cornutum).

Eragrostis cilianensis (stinkgrass) growing along side plot 12. Winter is nearing and the vegetation will soon be gone along with many of our smaller rodent species (some of which enter torpor during the colder months).

Monsoon showers bring summer flowers

Last month, September 30-October 5, a group of fellow Portal enthusiasts (Zachary Brym, Katherine Thibault, and Christa Weise) got together at the site to take on not only the rodent survey, but also the summer annual and perennial plant survey. Each experimental plot (50 m X 50 m) also has 16 (0.5 m X 0.5 m) permanent plant sampling quadrats within it so that we can understand what changes might occur in the plant community from year-to-year or based on differences in what rodents might be munching or moving around their seeds. We weren’t sure that we could actually finish the survey between our schedule flights to Arizona, but found that a determined group of (mostly) mammalogists could actually do pretty well at identifying desert plants!

There doesn’t seem to be a great field guide for the plant occurring at the site (barely in Arizona, almost in New Mexico, and a desert transition zone…) but we compiled a small ‘library’ to take out with us including a mini-herbarium of plants pressed over the years, the Flora of New Mexico book, Flora of Arizona Book (Epple), and the Peterson Field Guide to Southwestern and Texas Wildflowers, and a Grasses of Arizona Book. We’d love to hear any suggestions for other guide books for the area, especially for grasses or non-flowering ID characters.

The weather was great and by working all day everyday, we were able to sample all our rodents (still a desert pocket mouse takeover) and get to all the plant quadrates with very few unidentifiable individuals! The area near the Chiricahua mountains seems to have gotten more monsoon rain that many other areas of southeastern Arizona, so there were quite a few plants to count relative to some other years, and I would guess (haven’t finished entering data yet!) that there were about 15 species of annual plants per plot. This is actually relatively high diversity for this site, since many years have less than 5 species present! Most common was the Summer Poppy (Kallstroemia grandiflora), Woolly Tidestromia (Tidestromia lanuginosa), two species of spiderling (Boerhavia intermedia and torreyana) and panicum grass (Panicum arizonicum and hirticaule). We tried to photo document everything identified (and unidentified!) and hope to update our mini-herbarium soon since many of the samples are becoming worse for the wear.

It was a lot of work and a cobbled together fast trip, but we sampled everything and had a lot of fun!

This is a photo of plot 16 showing the vegetation this year. It may look sparse, but its a lot more vegetation than in the last few seasons!

Pit tagging a small desert pocket mouse, Chaetodipus penicllatus.

Kate gets reacquainted with the rodents.

Working on identifying plants in a quadrat, with Christa Weise.

Using the herbarium cards to identify a more rare species this year, Euphorbia micromera.

This is an unidentified carpetweed, Kallstroemia spp. It was really common this year...Any ideas?

Some of the grasses are tricky! We brought back samples of this one, but couldn't decide if it was Eragrostis arid or intermedia. We left the site leaning more towards intermedia.

Zack Brym, Kate Thibault, and Christa Weise work hard on an especially grassy sampling site.

We were lucky to get showers each afternoon to cool things down.

Portal Plant and mapping adventures

Last March, a team from our lab (Sarah Supp, Kate Thibault, Zack Brym, and Maria Brym) trekked down to Portal to take on the rodent and winter annual plant surveys, along with officially mapping all sampling points at the site. Up to this point, any spatial data at the site was estimated using aerial photos or roughly done using the regular spacing of stakes. We were able to use a super-accurate system (ProMark3 GPS units) to get GIS data reliable with less than 2 cm error!

Green points are plot corners, Red points are the corners of plant sampling quadrats (0.25 m2 each), and yellow are the rodent trapping stakes.

We’re excited to now have this data available and we are leaving this weekend to tackle the summer plant survey along with the usual rodent trapping.

The desert pocket mouse continues its takeover at Portal

After trapping rodents August 26-28, it looks like the desert pocketmouse (Chaetodipus penicillatus, pictured below) is continuing do really well, as almost all the other species appear to be doing not-so-well, at least at our site!

Above, the desert pocket mouse is in a plastic bag (photo by S. Cobbold), before we take its measurements. Since we never know what is going to be inside a trap, putting it in a clear plastic bag before handling it gives us a chance to take a look at the animal and to get a good grip on it so it doesn’t escape. Sometimes we catch larger rodents (which can bite!) or other non-rodent animals (which could be venomous!).

Portal has been known for having very high diversity of rodents compared to many other locations; however, if someone had just begun trapping there this year, they would have concluded otherwise. For over a year now, we have been mostly capturing the desert pocket mouse and Merriam’s kangaroo rat (Dipodomys merriami), with only a handful of other species present (i.e. one or two grasshopper mice (Onychomys spp.), Ord’s kangaroo rat (Dipodomys ordii), or cactus mouse (Peromyscus eremicus). This month, there were ONLY Desert pocket mice and Merriam’s kangaroo rat and not a single individual of another species! I think this may be the only time this has ever happened in Portal Project history.

Stephanie Cobbold, a  graduate student at Utah State University in the Jim MacMahon lab, helped out with trapping this month. She studies the sensitivity of species traits to habitat characteristics using spider communities, and we spent our free time looking for spiders, scorpions, and other small arthropods. Since there is a lot of vegetation right now, we saw lots of interesting webs and also saw a scorpion capturing a smaller scorpion! If you’re interested in this side of desert life, check out her great blog post on the spiders of Portal Arizona!

Above: Stephanie Cobbold learns the differences between handling spiders and rodents!

 

Centipede!

Stowaway: (noun) One who secretly boards a vehicle (e.g. aircraft or car), to travel without paying and without being detected.

I guess this centipede (Scolopendra polymorpha ?) decided it needed a vacation from the desert! When Stephanie Cobbold arrived back in northern Utah Sunday night with me after our field collecting trip at Portal, she got a bit of a surprise. When she opened her travel bag, a centipede popped out and raced across the floor. After 24 hours, she was able to find, photograph, and preserve it. From tip of tail to tip of antennae, it was about 5.5 inches, or 13 cm!

 

 

Kangaroo rat video

In September 2009,  a remote camera was set up near a seed tray put out by Kate Thibault and undergraduate students from Furman University who visited the site as part of their “wild semester“. Kate later strung the photos together to create this fun insight into a hungry kangaroo rat’s night. If you look close, you can also see some a grasshopper mouse (Onychomys spp.) traveling past. Footage takes place between 12:30 am and 6 am September 20th. Enjoy!

Summer in the desert

One thing that makes traveling to Portal each month so interesting is the speed at which the desert landscape can change. Southeastern Arizona has recently been in a major drought, but the arrival of summer monsoon rains seems to have helped green things up, at least temporarily.

Below, the first photo was taken on July 2, 2011 and the second photo was taken August 6, 2011. During that month approximately 11.4 cm of rain fell and transformed the dry, dusty ground into a carpet of green seedlings and flowers.

Some areas were covered in orange flowers (e.g., summer poppies, orange flame flower, and showy flame flower), purple flowers (e.g., silverleaf nightshade) and large caterpillars were abundant (I think mostly Sphinx moths).

In addition to the growth of new plant life, the summer rains have also led to flooding in the Chircahua Mountains where the fire left slopes unstable and vulnerable to washing away. Some of the forest roads remain closed and a short drive into Cave Creek Canyon makes it easy to see areas where the forest floor is buried under mud and debris washed down by flash flooding. Some locals, bloggers Azure Gate and Cave Creek Ranch, have posted updates and photos on conditions in the area.

In addition, the dry soil conditions and lack of vegetation on the bajada and in the valley seem to have allowed for increased erosion at our site as well. The gravel roads leading towards the Portal Project were washed out in places and erosion around the fenced plots meant that some gates were left > 12 cm above the actual soil surface or buried underneath mud and debris; both scenarios making it difficult or unlikely for rodents to actually find and use the gates. I’ll have to work at maintaining these gates over the next month as more rains are likely to occur.

Luckily, I had lots of help digging out rodent gates and collecting data by Elita Baldridge, a Ph.D. student in Ethan White’s lab who came to help out before we both headed to present at ESA after field work was finished.

I continue to be amazed at the “sea” of desert pocket mice (Chaetodipus penicillatus) that seem to be taking over–we’re even encountering control plots, where kangaroo rats should be dominant, with no kangaroo rats at all! Amazing.

Oh, and speaking of amazing…

Portal at ESA 2011

If anyone still reads this blog, you may be wondering whatever happened to Portal. Well, rumors of our demise are…mildly exaggerated. Since I last blogged here, intrepid volunteers stepped forward and helped keep the project running on fumes. If you’re a Portal fan and you’re going to be at ESA this year, you should give the following people a hearty pat on the back (or better yet, buy them a beer): Kate Thibault, Karen Mabry, and Sarah Supp  (Glenda Yenni  is also on this list, but she won’t be at ESA this year, so you can just toast her in absentia). From May-December  of last year, we held things together with spit, duct tape, and fervent wishes. I even funded one of the trips by selling  a bunch of books to those used textbook people who seem to habitually lurk  the halls. Fortunately, Mother Nature was working with us and rodent numbers were so low that we could scale back our trips to every other month because rodent pressure on the exclosures was very low. Then the funding deities took some pity on us and we were awarded a 2 year NSF grant to keep the rodent side of things running. We’re still operating on some spit and duct tape, but we’re no longer hyperventilating. The plant side of things are a little more dire, but we’re all doing what we can.

Things at Portal are so not dead, in fact, that we have 4 different Portal presentations occurring at ESA this year. If you’re interested in hearing what’s been going on at the site stop by the following talks/posters (with short promos taken from their abstracts):

Tues: Multi-decadal climate cycles and the dynamics of a Chihuahuan Desert ecosystem. Morgan Ernest, Thomas Valone, James Brown. Poster Session 4:40-6:30 PM in Exhibit Hall 3, Convention Center

One of the greatest challenges facing ecology is understanding shifts in ecosystems that are being reported across the globe. However, understanding whether a particular shift in an ecosystem is the result of directional anthropogenic influences is complicated by the discovery of long-term climate cycles, such as the Pacific Decadal Oscillation (PDO), that fluctuate between alternative phases on decadal timescales. Because many currently operating long-term studies were implemented in the 1970s, 1980s, and 1990s, many of these studies have collected data only under one phase of these decadal-scale climate cycles, making it unclear whether the long-term trajectories documented in some ecosystems represent long-term lagged responses to large-scale shifts in climate due to naturally occurring climate cycles.

Thurs: Small mammal activities decrease soil organic carbon storage in dryland ecosystems. Jane Smith, Heather Throop, Thomas Valone, Morgan Ernest, James Brown. New Mexico State University. 8:20AM Ballroom F, Convention Center

Most of what we know about the terrestrial carbon (C) cycle comes from research conducted in mesic systems and dryland C cycling dynamics are more poorly understood.  However, arid and semi-arid systems cover 40% of Earth’s land surface and may provide an important C sink that will help mitigate the accumulation of CO₂ in the atmosphere.  In drylands small mammal disturbances such as digging and burrowing can affect a large proportion of the surface soil, and these disturbances have the potential to influence inputs to and stability of the soil organic carbon (SOC) pool.  We asked how small mammal activity affects SOC pools in dryland ecosystems. 

Thurs: Experimentally altering biotic interactions has different effects on static and dynamic macroecological patterns. Sarah Supp, Xiao Xiao, Morgan Ernest, Ethan White, Utah State University. 4:00 PM Rm 8, Convention Center.

A major focus in recent ecological research has been to elucidate if and when the details of biological interactions play a critical role in producing observed patterns of diversity.  Macroecology has increasingly become an important and popular approach in ecology. However, because it often ignores the inherent complexity within biological systems in its attempt to find generality across systems, its utility has been increasingly questioned. This has generated an important question: are macroecological patterns contingent on the specific networks of interactions among ecological particles or do patterns emerge from interactions regardless of the details of interactions?

Friday: Decline in biotic resistance and the reorganization of an annual plant community by an exotic invader. Ginger Allington & Thomas Valone, Saint Louis University. 8:00 AM Rm 10A Convention Center

Species interactions are considered an important mechanism that limits the abundance and distribution of exotic species, a process known as biotic resistance. Many studies documenting strong biotic resistance have been conducted over short time scales. However, given time-lags inherent in exponential growth and natural population fluctuations, the strength of biotic resistance may change over time.  Here, we use a thirty-year dataset to show an eventual decline in the strength of biotic resistance.

Portal lives: a long awaited update

While I’ve been busy shirking my blogging duties over the past year, many people have been busy keeping Portal up and running. After we ran out of NSF funding last summer to fund research collection at the site, we were able to keep collecting data bi-monthly for the rest of 2010 on a shoestring budget and with a lot of help from Portal volunteers past and present. Luckily for us, rodent numbers remained extremely low throughout 2010 so maintaining rodent exclosures was not problematic, even with the decrease in trapping frequency. In addition, we were able to secure some funding for the next two years and began trapping each month again in January 2011. There is not a lot of money for incidentals, so we are continuing to use a combination of pit-tags and ear tags for individual markers until they run out and are keeping our fingers crossed that the trap shed and other necessary supplies can last a few more years.

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Trapping this year has been interesting–dealing with record cold temperatures, smoke from the Horseshoe 2 forest fire in Cave Creek Canyon, and a very pesky pack rat that seems intent on living in our trap shed and destroying as many trap box shoulder straps as possible. The spring and winter were extremely dry, combined with record-low temperatures in February, and there was almost no spring germination. Consequently, this past winter, rodent numbers once again dropped extremely low (20-30 rodents in the entire site!), but enough survived the last year to reproduce this spring and our numbers this summer have been >100 rodents on site. This is still a very small number compared to more productive summers only a few years ago and we have also seen a drastic change in species diversity at the site compared to a few years ago. We are currently capturing only 4 species–Merriam’s kangaroo rat (Dipodomys merriami; common), Ords kangaroo rat (Dipodomys ordii; rare), desert pocket mouse (Chaetodipus penicillatus; very common), Bailey’s pocket mouse (Chaetodipus baileyi; very rare), and southern grasshopper mouse (Onychomys torridus; common). In 2011, it seems like we are drowning in desert pocket mice (Chaetodipus penicillatus). In fact, there are plots where kangaroo rats (Dipodomys spp.) should be “king” and instead, we are ONLY catching desert pocket mice! Its all very surprising, but perhaps that is what makes Portal so interesting.