I can hear the cicadas buzzing outside, so I know it must be hot. The predicted high on NPR at dawn this morning was 99 degrees Fahrenheit. Not so warm for June in the Sonoran Desert, but uncomfortable. My fieldwork for several summers involved starting at dawn, but staying out all day in this, marking little seedlings on exposed hillsides. (You can see very preliminary – not peer reviewed yet – results of what I found at the Southern Arizona Buffelgrass Coordination Center website.) All summer. It was, well, tough. I have a rather unique data set as a result.
I was listening to the NPR weather report at dawn today because I was on my way to a field site to retrieve some plastic trays of seeds coated in fluorescent powder I had left out all night before. I am interested in the places nocturnal seed-eaters go. The wind picks up during the day, so I wanted to minimize the powdery spray between the time the seed eaters tracked it around, and when darkness falls and I can return to trace their pathways with blacklights (and friends!). I explained a little about the goals of the project in my previous post.
This dawn and dusk schedule is much more comfortable, convenient for me getting other writing done during the day, and also for attracting volunteers. Many animals adopt this schedule in hot deserts. The schedule even has a name: crepuscular, although I call it the siesta schedule. This will be key because I am detecting fewer pocket mice per night than I had hoped. So I may be in for many more crepuscular days of leaving little offerings to the desert, trying to increase my sample size.
Here is a teaser of the pocket mouse (genus Chaetodipus) jamming the fur-lined pockets next to its mouth full of seeds, then burying them nearby like a pirate with treasure, or a squirrel with nuts. Most animals that “scatterhoard” their seeds in many small caches near the source later return to move them to secondary caches, or even eventually to their “larder” in their burrow. I suspect these pocket mice behave in a similar way.
I did wonder, however, whether pocket mice (genus Chaetodipus, yes, the dancing ones), known for foraging under cover to avoid predation by owls, would tend to bury palo verde or other seeds under buffel grass (Pennisetum ciliare). Buffel grass is an invasive bunch grass spreading through the Tucson Mountains that inhibits native seedlings from establishing – and provides some nice cover to these mice, potentially attracting them to bury native seeds in the worst possible place: right under buffel grass.
To test this hypothesis, I left fluorescent-dusted seeds on fluorescent-dusted trays in the desert to see where mice would take the seeds, planning to return tonight with UV flashlights to follow their luminous footsteps. It felt like leaving sunset offerings to the tiny, dancing desert gods.
Much like the fantasy world of Game of Thrones, however, the Sonoran Desert has many gods who are more than happy to accept offerings. Most seed trays, it turned out, were visited by a roving band of javelina. Check it out:
You get a great view of their four-toed front feet, of their flexible snout at work, at their lumbering gait, and their curious investigation of the seed trays, marking flags, and cameras, and their powerful molars grinding the seeds of the foothills palo verde (Parkinsonia microphylla). One of the major reasons scatterhoarding rodents like pocket mice may be beneficial for the trees is that they protect some seeds from destructive consumers, like javelinas.
Often thought to be pigs, javelina are in a different family, although still related. This is an animal that is hunted for sport and meat, and is seen as a menace and a pest as it roves through town, knocking over trash cans. It lives in a wide variety of habitats, including even cloud forests and swamps as far south as Ecuador. Check out more information on them from the Arizona-Sonora Desert Museum, or visit in person to see some javelina yourself.
Driving down the Catalina Sky Highway from the summit of Mount Lemmon, Tucson looks at first like a dusty blond blur. As you approach the base of the mountain, patches of brilliant lemon resolve themselves.
As anyone with allergies knows, the palo verde trees (genus Parkinsonia) are blooming in force right now. But which neighborhoods are so infused with the native trees? Where do they start and end? From thousands of feet up, drawing patch lines seems trivial, but walk through the streets under the branches themselves, and you feel less certain. Is this block in, or does the patch start one more over?
You may begin to notice patches even within neighborhoods. At what scale should the palo verde patches be drawn?
The patch size of interest probably depends on your question. If you are seeking palo verde trees in Tucson to photograph (or seeking to avoid their pollen), a map with the raw number of trees per block might be helpful without trying to draw lines around patches. So why bother delineating these categorical zones at all? Why not measure some continuous variable, such as the number of palo verde trees on the block?
In other cases, a patch size itself is an important variable, so you have to stand back, squint your eyes, and draw the lines. The local invasive bunch grass buffel grass (Pennisetum ciliare), for example, grows outward in roughly circular patches. To track the rates of its spread in the foothills of the Santa Catalina Mountains, researchers have used repeated aerial photographs and traced polygons around the visible buffel grass patches.
I just returned from four days at UA Science Sky School, where we had snowball fights between the pines and aspens! There are no palo verdes to be seen on top of Mount Lemmon, which is a Sky Island, a little patch of pine forest in a desert sea. But where does that patch boundary lie? In fact, the vegetation changes in several dramatic and distinct zones as you travel up the mountain, but trying to pinpoint the transition point is an exercise in frustration.
The groups of students from Flowing Wells High School that I mentored this week at Sky School also had to confront these questions as they conducted field-based scientific research. To answer their question about how resources for plants (and animals) changed as a result of forest fire, we needed plots on either side of a burn boundary. The boundary of a fire seems abundantly clear until you are forced to locate a 10m x 10m plot right along that boundary.
Fortunately, the students in my group were focused on what characteristics mattered for their question. The question of where a boundary lies, at what scale, can be a very scaly problem indeed, and they resolved it by drawing a thicker boundary line between the burned and unburned areas, on either side of which the light, vegetation, and water availability was less affected by proximity to the other type of area.
Honestly, answer it. Here are a couple beautiful photos my friend Ty took to enjoy while you think about it:
What did you answer? And what did you take “people like you” to mean?
Your answer might depend on who you see represented in ads for outdoor brands, or in films at the Banff Mountain Film Festival, or who you see out on trails.
Or how often you yourself get outside.
There are lots of reasons some groups get out and enjoy nature more than others, which are beyond the scope of this post, but one factor is income (which is, of course, connected to many other factors). If you don’t have the money for a car (or gas, or gear) or the time off of a low-paying job, it can be hard to take your family to the nearest national park or wilderness area. If you’re not very healthy, or you have a hard enough time with daily life, the idea of tackling an optional challenge – physical exertion in a strange new place – may seem like a luxury.
And if you never have been out hiking, it’s sure hard to imagine yourself doing it. One way to solve that is to give more people (kids, families, everyone) the opportunity to leave the city and experience nature.
I volunteer with an organization through the Sierra Club, that recently changed its name from the 30 year old “Inner City Outings” to “Inspiring Connections Outdoors,” but the goal of the all-volunteer nonprofit is to give kids an opportunity to experience nature who might otherwise not get out of the city. Volunteers who have passed background checks and been trained in outdoor skills and first aid partner with Title I Schools, halfway houses, and other groups that work with at-risk and underprivileged youth to provide opportunities to go hiking, caving, camping, and stargazing.
The primary expense the group has is transportation costs for the kids, although when we can, we like to provide healthy snacks so everyone has had more than a bag of Hot Cheetos to fuel their adventure.
A group of MBA alumni from Arizona State University that have an annual tradition of hiking the Grand Canyon Rim 2 Rim 2 Rim (47 miles and change… and a lot of elevation change!) are using their trip to raise money for this group. I appreciate these guys who feel they belong in the backcountry raising funds (and awareness) to help a new generation expand that pool of people who feel they belong there, too.
Want to kick in to support getting underserved youth outdoors in the Tucson area? Donate to their campaign: https://www.crowdrise.com/r2r2r2015/fundraiser/
And in somewhat a related note on representation in the outdoors community, for women who are annoyed that skis made for women’s sizes and shapes are often of lower performance aimed at intro-level skiers and snowboarders rather than the advanced and expert, check out this kickstarter of high performance skis and boards for women (sans the pink flowers, as a bonus!):
Fortunately, the observations I wrote about in January were made at the site of a long term experiment on the interactions of rodents and plants. Ecologists have collected thirty-eight years of data on rodent reproduction, along with systematic data on weather and plant life.
Erica Christianson, a doctoral student at Utah State University, is studying these interactions at Portal as part of her dissertation work, and she crunched some of the numbers on reproduction and weather conditions (and generously allowed me to share them here!).
Erica’s main hypothesis, and one I wondered about in January, was that the large rainfall in the late summer and early fall last year resulted in more seeds available in early winter. With sufficient energy to stay warm and active during the winter, females could afford to breed.
A very quickly constructed scatterplot reveals that years with higher rainfall in the late summer and early fall do indeed have higher rates of female reproductive activity observed the following January:
You might notice a couple of things about this plot. First, you would be justified in pointing out that this is a correlation, and does not prove that the summer rain causes high January rodent reproduction. But it is consistent with a reasonable explanation for it.
You might imagine designing an experiment to test the causality more directly, in which all the plants are killed before they produces seeds after the next year with high summer rainfall. That would be an ambitious experiment on this landscape, involving a lot of person-hours with some herbicide or clippers, but it could be done.
You might also notice that fall precipitation does not perfectly predict female reproductive activity. Probably that interacts with several other factors. Ever noticed how you get hungrier in cold weather? Your body burns more calories to stay warm. (This is why mountaineers are advised to continue eating as much as possible if caught out overnight on a cold peak.) I suspect that if we also looked at the temperatures each winter, we might find that less rain is required in warmer winters to boost female reproduction, and the rainfall plus temperature would explain even more of the variation in reproductive activity. But that probably best left to future posts.
I should also point out that these results are extremely preliminary. Typically, to have some confidence in a conclusion, the full description of the methods for data collection and analysis should be subjected to peer review – that is, at least three or more other experts will critique it before it is published. That’s definitely not how my blog works.
If you are interested in getting out in the field to collect data used in real long term and large scale research projects, check out iNaturalist, National Phenology Network, and the Arizona Sonora Desert Museum. If you are in Tucson this weekend for the Tucson Festival of Books, visit Science City to meet some of these folks in person and pick up brochures for other Citizen Science opportunities as well!
[Updated 3/17/15: I changed the label on the x axis of the grass from “Fall precip” to “late summer” to more accurately reflect how the plants seemed to respond to the rainfall and be more consistent with my text.]
I first heard this phrase from my friend, Brad Boyle, last weekend (though he was cheekily commenting that the plural is data). An anecdote, in case you’re not sure, is a story about something that happened, usually to you or someone you know. It might be something you noticed once, or even a number of times. And that provides you with some information. But that does not necessarily make it data.
Data is information that should be collected and analyzed in a standardized way to answer a question or estimate some value (like the growth rate of a population or the strength of a bridge). One problem with anecdotal information is that it is not collected with the intention of providing a large or unbiased sample. Basing our understanding of the world around us on anecdotal information could lead us to the wrong conclusions, resulting in poor decisions.
For example, many medical procedures have variable outcomes. Imagine you have some inflammation of the elbow (lateral epicondylitis) from playing tennis, rock climbing, or just everyday life. Corticosteroid injections seem to be the most effective way to get a short term reduction in pain and inflammation so that you could use that elbow in the next few weeks. However, the study I linked to reported a 92% success rate at the six week mark. What if you had a big competition coming up and wanted to decide whether to go for the treatment? If you talk to only your aunt, who had had the procedure, and was part of the 8% it did not help, you might decide not to get it. Especially if you heard a second anecdote from your best friend, who was also not helped! There you have multiple anecdotes, but a larger sample might reveal there is a pretty good chance it would help you be able to compete.
Understanding the scientific method is important for everyone, not just scientists. If your vacuum cleaner breaks, to borrow an example from another friend, Marielle Smith, scientific thinking can help you to fix it more efficiently. Instead of replacing parts at random, you might form a hypothesis about what piece failed. That hypothesis might be based on anecdotal information, like what part of your friend’s vacuum cleaner broke. Or it might be based on observations, such as where smoke is emerging from. Either way, you can test your hypothesis by isolating that part of the vacuum to test it, or by replacing it and trying the vacuum, ultimately spending less time and money than replacing parts at random.
Question everything. Question sources, and learn who has the expertise to be right about a subject. Just as a theoretical ecologist might not have the skills to remodel a kitchen professionally, a lobbyist with no scientific training may not have the skills to validly contest a research finding. Make up questions while you’re driving (or biking) to work, or waiting in the grocery store check out line. Just be curious about the world.
6. Use science to shape how you communicate with people around you.
There are very rational reasons that people may not have all the data or scientific interpretations on a topic, like vaccinations. Going out and doing research takes time and effort, and people have lives to live. Researching every little thing is impossible. So instead, we lump issues together into our identities to decide how we feel about them. Cognitive science has demonstrated that attacking a person’s beliefs, or implying that she or he is an idiot for not knowing something, is the best way to solidify a previously held belief. So when engaging with someone less scientifically literate than you, use what evidence suggests is the best way to get them to change their beliefs: acknowledge their fear or doubt are real and reasonable, acknowledge that data and scientific papers are often not open access, and… ask questions.
Last weekend, I peeked at the naughty bits of dozens of rodents. I was in the San Simon Valley, outside Portal, Arizona, at the site of a long term ecological project there. (Incidentally, a fantastic stargazing site as well! Thanks to Alan Strauss and his friends for letting the mammal studying group join them and their telescopes for a little while.)
A student from Morgan Ernest’s lab was trapping rodents and tagging them, as she does every month. I had joined them to compare the rates at which motion detecting cameras caught animals with the rates that the live traps caught animals. For example, here is a video in which the camera recorded a visitor that did not get caught in the trap:
When animals are caught, they are measured and tagged. Rodents’ genitals become enlarged when they are open to mating, so researchers with a live mouse in hand can easily see if it is physically ready to be reproductively active. Typically, rodents reproduce primarily during the warm months, from March to October. Since this was mid-January, I was surprised to see many females pregnant or lactating as if having recently given birth, males with enlarged sex organs, and even recent signs of mating in a female kangaroo rat. No one has yet examined the data to see if this is really an unusual number of reproductively active animals, but it seemed high to me, though I am not an expert.
I had always thought the cold temperatures increased the risk of freezing to death, and that was why they bred in the summer months. But 2014 was the hottest year since record keeping began in 1880. Could the animals simply feel warm enough to be active and to give breeding a go?
Another important factor in both reproducing and staying warm is food energy. I recently went backpacking in southern Utah, hiking frequently through snow, and was amazed at how many calories I could – and needed to – eat to stay warm and active.
Substantial rains this summer at the Portal site made it the grassiest I have seen it in about five years. All that grass produces a lot of seeds, which many of these animals eat. Perhaps the larger amount of energy available is giving them the energy to go for it in January.
It is impossible to know if any one specific instance is a result of a long term trend in an otherwise variable system. Is the number of reproductively active rodents in January outside the typical range? Or even unusually high at all? Is it unusually high for grassy years? Is this one more small sign of larger changes in our climate?
If you have noticed small changes like this over the winter, I would be very interested to hear your stories.
Last week, I posted about my encounter with the impressively aggressive and carnivorous mice (Onychomys), which ended in me leaving a number of motion-sensing infrared video cameras at a long term ecology site near Portal, Arizona. I’m happy to report I have some footage of these mighty hunters. (The team from the Ernest lab had trapped a number of Onychomys they ID’d as species torridus on the plots where I placed these cameras just nights before, so my educated guess is that these videos are of O. torridus, but if any mammologists can distinguish the species more definitively from these videos, I’d love to hear about it.)
I baited the cameras with mixed birdseed, so I had lots and lots of videos of granivorous (seed eating) kangaroo rats and pocket mice to view, like these:
But about an hour after the pocket mouse (above) was last seen walking through that path in the grass, look who followed:
The southern grasshopper mouse (I think)! Also known as the scorpion mouse, because it takes down all kinds of dangerous and venomous arthropods, as well as animals nearly its own size. And ten minutes later it (or another one, can’t tell for sure) came back through again, definitely looking like it was tracking something:
Wait, why did I bait the cameras with birdseed when I was seeking carnivorous animals? Although grasshopper mice are carnivorous, they are commonly captured in live traps baited with seeds and oats. I had wondered whether they were at all interested in the seeds, or whether they smelled animals previously trapped in that box and were looking for prey – or whether they were just curious and exploring. (Plus, I was secretly hoping I would capture a grasshopper mouse killing the pocket mouse that was eating the bait. No luck.)
One video seems to answer my question: even if these mice can be completely carnivorous, some are open to trying new food:
I hear a certain large foreign TV network is working on a documentary about these animals. To get high-quality video images, they have to capture a number of animals, then stage encounters by placing a grasshopper mouse and, say, a tarantula in a sandbox together. I like to think that although my footage is less polished, it provides a complementary view of their lives by peering at what happens on a daily basis out in the wider world, where anything could happen.
Last weekend, I drove from Tucson down to a long term ecology research site near Portal, Arizona. It’s a site started by Jim Brown in 1977 with a series of fenced plots that look at the effect of rodents on the plants of the Chihuahuan Desert, now run by Morgan Ernest’s lab. It looks substantially different than the Sonoran Desert that I’m used to, but still spectacular laid out at the foot of the Chiricahua Mountains.
I was helping out with the monthly rodent census at the sites. Researchers from Utah State University travel to the Portal Site for a long weekend every month to live trap and mark small mammals. I was also interested in comparing camera trap encounter rates with live trap rates as the seasonal and inter-annual population density fluctuations occur, so I set up my cameras, after dark, on the first night I got there. (Yes, I also wanted to see if the pocket mice near Portal dance. I suspect they do.)
While I was setting up the cameras in the dark, I thought I heard the faint squeal of a truck’s breaks. It lasted maybe two seconds. But no headlights were visible in the dark San Simon valley. I heard it again and again as I walked around a quarter hectare plot, setting out cameras.
It turns out the squeal is actually an itty bitty howl, emitted by the only genus of carnivorous mice. Yes, if you thought mice were scary before, just think of an aggressively hunting mouse standing on its hind legs to howl upward at the sky. They have short, stubby tails, and typically eat, well, grasshoppers, I guess. It is grasshopper season in Portal, and the horse-lubbers especially cover every surface, and are slow to move or respond. Easy prey.
However, one of the other grad students had a story of releasing a Bailey’s pocket mouse (an animal weighing about 20 grams), and seeing a recently released grasshopper mouse (about 25 grams – not much larger!) seize it by the throat and drag it down a hole. They must be at least somewhat omnivorous (eating things other than meat), because we caught several in the Sherman live traps that were baited with millet seed.
Wikipedia claims they have home ranges of approximately 28 acres and are very territorial, but we caught three in less than a quarter hectare. But they certainly move differently than the pocket mice and kangaroo rats that made up the bulk of the captures. Those others (in family Heteromyidae) are boing-y, bouncing around, like, well, a kangaroo. The grasshopper mice, when released, scurried off through the grass in a more fluid, slinky way, like a cat or a ferret, using all four feet and close to the ground.
I plan to pick up my cameras next week. I look forward to seeing what video – and audio – I have of the unique species there.
The first time I saw the Biosphere 2 space frame structure, it reminded me of a giant jungle gym. Actually, every time I see Biosphere 2, it looks like a giant jungle gym. I’m sure I’m not the only one who stares at it, imagining how to to climb it.
It’s just that I finally got to.
In my last post, I wrote about a summer excursion to the Brazilian Amazon to help with research on the future of the Amazon under climate change. I was helping Neill Prohaska and other members of Scott Saleska’s lab and the GO Amazon project measure seasonality and reflectance of leaves, which is part of a larger effort to understand what would happen if the climate there gets hotter and drier.
But back in the early 1990’s, Biosphere 2’s original builders included a tropical rainforest in their structure. Now researchers can do the experiment by creating a drought for an entire stand of living rainforest trees, which is tricky to do in the Amazon. In fact, they kind of already have.
Over the years, as the facility changed hands, it experienced a gap during hot Arizona summers with virtually no air conditioning or rainfall – an extreme version of climate change. Another member of Scott’s lab, Ty Taylor, has analyzed the concurrent change in the tree species remaining. (I should point out that the species in B2’s forest are not all Amazonian, but from around the world, so it’s not a perfect analog in several ways.)
But Dr. Joost van Haren wants to know what happens to individual trees and to the system’s ability to photosynthesize and grow, storing carbon dioxide from the air, during a drought. So for the last 8 weeks, the B2 tropical rainforest has experienced a drought. This weekend, I was part of a small team that helped take some vital rates of photosynthesis activity in the rainforest.
By far the most exciting part was the pre-dawn climb up through the space frame to cut sample branches. I was actually not helpful at all in this part – Neill scampered around the structure like a capuchin, while I moseyed upwards comparatively like a sloth. I didn’t cut a single branch.
It turns out when you approach the space frame closely, the struts are a little bigger than your school yard jungle gym, a little slicker with condensation (even during the drought they were a little wet), a little more likely to be covered in vines to catch you…. and the whole thing is a little bit taller.
And while we used harnesses and safety devices that clipped to these struts, these static lines would hurt to fall on, even if you didn’t break a bone hitting the bars of the frame on your way down.
“Don’t fall,” Neill told me. Eek!
I didn’t fall, even climbing all the way to the top of the rainforest section to watch the sunrise, where a bird flew in through an open vent and perched on the struts nearby.
If YOU haven’t seen the rainforest for a while, you should join me some Saturday evening in October out at Biosphere 2 for pizza, live animals, telescopes, and more. This is a shameless plug, since I’m helping to coordinate these Discovery Nights, as the late evening events are called, but seriously, you should get some friends together and go. I’ll be at all three. There will be live animals, fossils or meteorites, telescopes, and the chance the wander through B2 in the dark at your own pace instead of with a large tour. Oh, and your admission fee includes an annual pass on those nights. And kids are free. (If YOU want to get in free as well, you can volunteer all evening! Send me an email ASAP if you want in.)