Trowbridge’s shrew

Over the holiday I visited the western Cascades with old friends from Ashland. We stayed in a forest service cabin at the Fish Lake Remount Station – an historic waypoint on the Santiam Wagon Road. The wagon road was once a thoroughfare for pioneers crossing from the high desert to the lush Willamette Valley. Climbing between high volcanoes, Mount Washington and Three-fingered Jack, the road crossed many lava flows. These must have been tough on wooden wagon wheels. Now the road is a pleasant walking trail. Near the head of the McKenzie River it passes through evergreen forest dominated by Douglas fir.

At the intersection of the Santiam Wagon Road and the McKenzie Trail we saw a tiny gray shrew scurrying haphazardly over the path. Last week was clear and cold with temperatures below freezing, and much of the ground was frozen. Shrews are burrowers, and this one may have found itself above ground and unable to retreat. Based on the location where we found the animal, the lack of contrast between the belly and back, and the strongly bicolored tail, I think that our shrew was a Trowbridge’s shrew (Sorex trowbridgii).

Shrews appear in the fossil record 160 million years ago. At that time, the high Cascades were being pressure-cooked hundreds of miles beneath western North America, and dinosaurs like Allosaurus haunted the continent’s riverways. Shrews were, and still are, primarily eaters of invertebrates, though Trowbridge’s shrew also partakes of Douglas fir seeds. This diet does the shrews little good when they are caught in live traps baited with peanut butter and oats; they frequently die.

I can only guess about the name “Trowbridge”. Sorex trowbridgii was named in 1857 by Spencer Baird (1823-1887). In 1854, William Trowbridge (1828-1892) donated a large collection of fishes to the Smithsonian, which Baird curated. Did Baird honor the ichthyologist William Trowbridge by naming an obscure western shrew after him? Or was it a joke? Maybe Trowbridge wore something resembling a shrew pelt while receiving an award. I would love to know.

 

Sources:

Alt, DD and DW Hyndman. 1978. Roadside geology of Oregon.

A shrew in the high Cascades. Sorex trowbridgii?

A shrew in the high Cascades with a bicolored tail and little contrast between back and belly. Sorex trowbridgii?

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Frozen basalt. Bad for burrowing.

Frozen basalt. Bad for burrowing.

 

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Why not fire truck berries?

In the fall, many plants in western Oregon (and elsewhere) produce brightly-colored fruits. These attract fruit-eating animals, which eat the fruits and move their seeds to new locations, potentially better sites for germination and survival. By and large, such fruits are red, blue, or purple – colors that contrast with surrounding vegetation and appeal to birds, but snowberries (Symphoricarpos albus) buck the trend, producing white fruits about the size of huckleberries that dangle on the ends of flimsy stems.

Snowberry (Symphoricarpos albus), a shrub with unique, white fruits.

Snowberry (Symphoricarpos albus), a shrub with unique, white fruits.

Why are snowberries white when so many other plants produce red berries? If the red of other fruits has been selected to enhance seed dispersal by birds, maybe the white of snowberry has been selected for dispersal by another agent. In the tropics, white or green fruits are commonly eaten by bats. Flying through a dark forest, a bat may detect a white fruit more easily than a red one, particularly if it has a strong odor and is hanging at the end of a long branch. Unfortunately, there are no tropical fruit bats in western Oregon*, but there are nocturnal fruit-eaters. Perhaps woodrats or flying squirrels cue in on snowberries.

Alternatively, snowberries might be white because why not? Presumably red fruit pigmentation exacts some energetic toll from plants, so all else being equal, a white fruit should cost less than a red one. Pheasants and turkeys appear content to eat unadorned snowberries, and some of their seeds are able to germinate following gut passage**. Selection on snowberry’s dispersal mechanism may also be weaker than for other plants; S. albus seems to reproduce more commonly via spreading rhizomes than from seeds.

 

*Though a vampire bat in the same family existed in northern California during the Pleistocene.

**Based on the results of a seed viability study from turkey feces conducted by Sara Evans-Peters at OSU.

More snowberries

How did this snowberry get to Jackson-Frazier Wetland?

A more common

Rose hips: targeted advertising for visually-oriented consumers.

 

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Night Fliers

From September 17 through November 3, the G2 Gallery in Venice, California will feature an exhibit called Night Fliers, which will display photographs of bats, including some of my own taken during fieldwork in southern Costa Rica. I am excited to have my photographs included in this display for a variety of reasons, not the least of which is that I have long admired Christian Ziegler’s nature photography, which will also be featured in the exhibit.

More importantly, bats are often not as easy to appreciate as some other kinds of organisms, like birds or butterflies. Without specialized equipment and training, bats in the wild can just seem small and dark, prompting awkward questions like Are they birds or insects? and They’re all blood-sucking vampires, right? Photography is one way that the interesting and diverse natural histories of bats can be captured and revealed widely.

In that spirit, here are a few tropical bat photos from my 2012 field season.

Spix's disc-winged bat (Thyroptera tricolor) at Piro Biological Station on the Osa Peninsula in southern Costa Rica. Disc-winged bats are so-called because they have suction cups on their wrists and ankles that they use to hang onto the inside of young, rolled-up leaves of tropical plants like Heliconias. As the leaves get older, they unfurl, stripping the bats of their hiding place. Disc-winged bats maintain group cohesion using a Marco Polo-esque call-and-response system between bats that have found a new leaf to hang out in and bats that are flying around seeking their companions.

Spix’s disc-winged bat (Thyroptera tricolor) at Piro Biological Station on the Osa Peninsula in southern Costa Rica. Disc-winged bats are so-called because they have suction cups on their wrists and ankles that they use to hang onto the inside of young, rolled-up leaves of tropical plants like Heliconias. As the leaves get older, they unfurl, stripping the bats of their hiding place. Navigating life between these ephemeral refuges, disc-winged bats maintain group cohesion using a Marco Polo-esque call-and-response system between bats that have found a new leaf to hang out in and bats that are flying around seeking their companions.

Many people in Latin America think that all bats are vampire bats that suck blood. This is not true. There are more than 110 bat species in Costa Rica and they have a diversity of life histories. Costa Rican bats may feed, for instance, on insects, fruit, nectar, fish, frogs, birds, other bats, or the blood of birds and mammals. If everyone could feed a piece of watermelon to a Heller's broad-nosed bat (Platyrrhinus helleri) from their hand, such misconceptions would quickly fade away.

Many people in Latin America think that all bats are vampire bats that suck blood. This is not true. There are more than 110 bat species in Costa Rica and they have a diversity of life histories. Costa Rican bats may feed, for instance, on insects, fruit, nectar, fish, frogs, birds, other bats, or the blood of birds and mammals. If everyone could feed a piece of watermelon to a Heller’s broad-nosed bat (Platyrrhinus helleri), such misconceptions would quickly fade away.

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This is a Jamaican fruit-eating bat (Artibeus jamaicensis), one of the biggest bat species that we caught in Costa Rica. An interesting fact about this species is that it exhibits lunar phobia – timing its feeding bouts to correspond to the darkest nights or hours when the moon isn’t very bright. It might more apt to call this condition owl phobia.

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This Myotis is one of the smallest bats that we caught. The genus Myotis is made up of insect-eating bats that catch their prey in mid-air. Unlike the leaf-nosed bats, bats in this family (Vespertilionidae) are more diverse in northern latitudes than in the tropics. The adaptation that allowed this family to diversify in the cold north is hiburnation – a good strategy that has recently become a bit of a liability for some species.

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Nectar bats prefer juice boxes to watermelon. This orange nectar bat (Lonchophylla robusta) one was particularly fond of the pera. One species of nectar bat (Anoura fistulata) has a tongue so long that it has to be stored inside of its rib cage.

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The common vampire (Desmodus rotundus) gives other bats a bad name by feeding on mammalian blood, occasionally including the blood of Hominids. Vampire bats have modified front teeth that are very sharp which they use to create small lacerations on larger animals (often cows). Their saliva contains an anticoagulant that maintains blood flow. A farmer in Costa Rica told me that the pioneers used to tie a cat at the foot of their baby cribs to keep away vampire bats.

 

 

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Artificial Bat Roosts for Tropical Forest Restoration?

Artificial bat roost. Photo by David Douterlunge.

Artificial bat roost. Photo by David Douterlunge.

Fruit bats are very good at dispersing tree and shrub seeds into disturbed tropical ecosystems. We wanted to know how we could attract more of them into everyone’s favorite disturbed ecosystem – the abandoned cow pasture. In a paper in Biological Conservation, Ellen Holste, Zak Zahawi, and I describe an experiment in which we placed artificial bat roosts in pastures and forests in southern Costa Rica. The roosts were designed to simulate tree cavities, which many bats use for sleeping and feeding. We monitored the roost boxes for two years and found that fruit bats visited roosts in forests sooner and more often than roosts in pastures. When bats did use the roosts, seed dispersal increased dramatically, but the number of seedlings did not change. We conclude that artificial roosts in our area did not accelerate forest succession. Thanks to Juan Abel Rosales and Román Gómez for their help with this project.

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Tallgrass prairie restoration

This week I attended the annual meeting of the Ecological Society of America in Minneapolis, Minnesota. Over the course of four and a half days, thousands of ecologists presented their work to one another in short talks, posters, and informal conversations. Paradigms were questioned, collaborations were struck, and job opportunities were sought.

A personal highlight was an informal field trip to a prairie restoration site in the Cowling Arboretum at Carleton College. About a dozen ecologists (many from UC Davis) came along, and their breadth of expertise made for an engaging walk.

We stepped out of the cars into a sunny, unseasonably temperate afternoon. A few mosquitoes hovered in the shade of the woods along the Cannon River. A Great-crested Flycatcher gave a loud wheeep from the canopy. Matthew Kaproth from the University of Minnesota showed me that the small seeds of jewelweed are edible. They taste like walnuts.

Bur Oak (Quercus macrocarpa) Savannah and tallgrass prairie at the Carleton Arboretum.

Bur Oak (Quercus macrocarpa) savannah and tallgrass prairie at Cowling Arboretum.

The prairie was at its peak growth during our visit with big bluestem, indiangrass, and switchgrass growing head-high. The color spectrum was saturated with purple mints, yellow compass flowers and black-eyed susans, red grasshoppers and dragonflies, blue swallows, and orange soldier beetles.

Goldenrod soldier beetles (Chaliognathus pensylvanicus) mating on a rattlesnake master (Eryngium yuccifolium).

Goldenrod soldier beetles (Chaliognathus pensylvanicus) mating on a rattlesnake master (Eryngium yuccifolium).

According to Jens Stevens, compass flowers (Silphium laciniatum) align their foliage north-south, minimizing solar radiation in midday.

According to Jens Stevens, compass flowers (Silphium laciniatum) align their foliage north-south, minimizing solar radiation in midday.

Compass flower leaves, properly oriented.

Compass flower leaves.

The prairie restoration site sits near the northern edge of the Great Plains. Hardwood, deciduous forests dominate across the Cannon River and up through the Twin Cities, transitioning to boreal forest in the northeast part of the state. Seeds for the restoration came from local railroad right-of-ways. Perhaps fires along the railroad beds maintained the native plant communities as other lands were plowed under for agriculture. Prescribed fires in the spring every few years now maintain the prairie.

Thanks to Jens Stevens for organizing the fieldtrip and to my hosts Dan and Tess for their great hospitality.

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Big Basin still blooming

Fairy lanterns (Calochortus albus)

Fairy lanterns (Calochortus albus)

The coastal grasslands are already drying up and turning brown, but Big Basin still sports an array of wildflowers. Hiking down the Skyline-to-the-Sea Trail yesterday, Jorge Torres, Myriam Scally, and I found several populations of fairy lanterns and walked past carpets of Pacific starflower.

Foxglove (Digitalis purpurea)

Foxglove (Digitalis purpurea) – a naturalized flower so beautiful that it will make your heart stop (or not). Note the white spider on one of the petals.

Pacific starflower (Trientalis latifolia)

Pacific starflower (Trientalis latifolia)

 

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Are migratory birds more likely to strike windows?

The house that I rent in Santa Cruz has several large, plate glass windows. From time to time I find a stunned bird sitting below these windows, and more often than not the bird is migratory. Although I don’t keep a record of window strikes, my recollection is that three birds have struck the windows so far in 2013: one Red-breasted Nuthatch and two Pine Siskins (including one this morning). Both of these species breed in northern coniferous forests and winter on the central coast of California (some Red-breasted Nuthatches also breed locally). This observation makes me wonder whether migrants are more likely than residential birds to hit windows.

I would not be surprised to learn that there is natural selection for birds that are better at detecting windows. It’s been estimated that one in two window strikes will kill a bird, and this kind of mortality should exert a strong selection pressure for birds that are frequently exposed to window-striking opportunities. Since the residential birds in my yard, like Lesser Goldfinches and Pygmy Nuthatches, are here all year, presumably they deal with reflective glass more frequently than their cousins that spend much of the year in the vast windowless wilderness of the boreal forest. (A friend wryly suggests that this hypothesis could be tested by installing plate glass obstacles in Canadian forests).

For an interesting discussion of the impacts of reflective skyscrapers on birds during nocturnal migration, see this piece about Toronto by New York Times writer Ian Austen.

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Self amputation at Fort Ord

An influential scientist once told me that much of biology can be basically boiled down to poop and sex. In pursuit of the former, I found myself over the weekend at Fort Ord, a University of California Natural Reserve in Marina. Fort Ord protects a live oak forest and adjacent sandmat manzanita chaparral. The objective of the trip was to study the scats of medium-sized carnivores, such as coyotes, bobcats, and foxes. This is a central component of my wife’s doctoral research. As with most scatologically-oriented researches, her project is designed to learn about who eats whom in nature.

A related topic is how different animals try to keep themselves from being eaten. In late afternoon near the entrance to Fort Ord, Rachel and I saw a raven cornering an alligator lizard against the concrete curb at the edge of the road. The raven danced around the lizard, which stood with its back against the wall and its mouth open aggressively, staring death in the face. After a short tussle, the raven took off with a large piece of lizard meat writhing in its talons. The rest of the lizard skittered away into the chaparral, stunned but alive.

What we witnessed was the lizard’s self-amputation of its own tail. This predation-avoidance tactic is called autotomy; the idea is that if you’re a lizard under attack, you drop your tail as a distraction to the predator. The tail continues to flop around as though it were still alive, and meanwhile you make a break for the nearest cover. (If you don’t believe that it works, take a look at this youtube video.)

Lizards and skinks are frequently associated with autotomy, but a variety of other animals also employ this strategy. Known autotomizers include slugs (though not our local bananas), spiders, molluscs (including octopi), crustaceans, and bees. In the case of spiders, the appendages cast off are legs rather than tails, and the function may be to prevent envenomation (by wasps, for instance) rather than to avoid predation. Not surprisingly perhaps, research in arachnid autotomy has found that spiders are more likely to discard legs when a researcher injects “painful” substances into them rather than non-painful ones.

In bees, the discarded appendage does not have seven replicates to fall back on; during copulation, male honeybees turn their entire reproductive tract inside out and leave their genitalia inside of the queen.

Sandmat manzanita (Arctostaphylos pumila) at Fort Ord Natural Reserve.

Sandmat manzanita (Arctostaphylos pumila) at Fort Ord Natural Reserve.

Our quarry - coyote scat.

Our quarry – coyote scat.

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Zea squamata

Walking home from school yesterday, Rachel and I stumbled upon an alligator lizard sunning herself on the trail. Her eyes were fiery orange, and her back was colored like indian corn. She held her legs close against her sides. Possibly she had been undulating like a snake through the adjacent field, as alligator lizards are known to do. I say she because this individual had a slender head; male alligator lizards possess massive jaw muscles, giving their heads a triangular shape.

Southern alligator lizard (Elgaria multicarinata)

Southern alligator lizard (Elgaria multicarinata)

Two species of alligator lizards can be found in Santa Cruz: the northern (Elgaria coerulea) and the southern (E. multicarinata). Though similar in many respects, the northern and southern alligator lizards differ in their reproductive strategies. Southerners, like many other reptiles, are egg-layers, but northerners are viviparous, meaning that they give birth to live young.

Vivipary crops up here and there throughout the lizard family tree. One reasonable explanation for the difference between Santa Cruz’s two alligator lizards is that the northern species commonly experiences colder temperatures and shorter summers than the southern species. Rather than deposit her eggs in a spot that might be too cold for them to hatch, a northern female might be better off keeping her eggs inside her body and seeking out sunlight in which to bask and regulate the temperature of her progeny. A southern female, in contrast, can lay her eggs in a warm burrow and get on with her business.

A close-up of the checkered back

A close-up of the checkered back

Southern alligator lizard at Pinnacles National Park

Southern alligator lizard at Pinnacles National Park

Defensive posturing by a southern alligator lizard in Pogonip State Park

Defensive posturing by a southern alligator lizard in Pogonip State Park

*For a good comparison of northern and southern alligator lizard field marks, check out californiaherps.com. You can also look at the Natural History of the UC Santa Cruz Campus for more detailed information about their reproductive habits.

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An unexpected wattle

For the past two years, I have walked through Cave Gulch and across a patch of chaparral nearly every day on my way to school. I almost always take the same route, and I generally pay attention to my surroundings (a blooming Trillium here, a fresh scat there), so I was surprised last week to find a tree that I had never before seen.

I was first drawn to the tree by its puffy, white flowers, but what really piqued my curiosity were the leaves. Unlike other local foliage, these simple leaves were asymmetrical and had nearly parallel veins. I tried to identify the tree using several keys, but ultimately I had to fall back on a higher authority. I sent a photo of the leaves and flowers to my lab-mate Mike “The Manzanita Maniac” Vasey who clarified the problem in short order.

Acacia melanoxylon

White, puffy flowers of Acacia melanoxylon

In its homeland of eastern Australia and Tasmania, my mystery tree is commonly referred to as a wattle, but in the U.S. people know it as Australian blackwood (Acacia melanoxylon). As an Acacia, this plant is a member of the world’s largest tree genus; Acacia contains over 1200 species and is found on every continent except Antarctica. California has its own native Acacia in the southern deserts (A. greggii), but blackwood is a relatively recent arrival, presumably brought to California for forestry or landscaping.

Mike also pointed out to me that the “leaves” I was looking at are actually phyllodes, or flattened leaf stems, modified to perform the functions of the real leaves that are nowhere to be seen. The Acacias that I am more familiar with in Central America generally have compound leaves with veins branching from central midribs on each leaflet. Apparently blackwood does too, but only as a young seedling.

Modified leaf stems, phyllodes, that look and function like leaves

Modified leaf stems, phyllodes, that look and function like leaves

Why trade your leaves for phyllodes? In dry climates, plants must maintain a tricky balance between photosynthesizing and conserving water. In order to turn sunlight into energy, plants exchange water vapor for carbon dioxide through tiny pores called stomata. Plant tissue with more stomata can do more photosynthesis, but it also loses more moisture. Because phyllodes are modified leaf stems, they have fewer stomata than normal leaves, so they lose less water during photosynthesis – a nice adaptation if you live on the world’s driest continent.

Acacia melanoxylon growing at the intersection of North Fuel Break and Red Hill Road

Acacia melanoxylon growing at the intersection of North Fuel Break and Red Hill Road

Last year's curly seed pods, and this year's flowers, which have already turned brown

Last year’s curly seed pods, and this year’s flowers, which have already turned brown

 

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