August 2, 2016
Los Angeles is a stunningly metamorphic place. A vast, industry- and people-dense metropolis, L.A. lives in the global psyche as the frontier of opportunity and personal transformation. Everything about L.A.—its geographic boundaries, the contours of its built environment, the languages and culture and impulses of its residents—is in a permanent state of flux. The city becomes nearly unrecognizable from one generation to the next. Our planet is in a state of equally dramatic transformation. The Earth is rapidly being reconfigured into sprawling urban centers, like L.A. According to the World Health Organization (WHO), “The urban population in 2014 accounted for 54% of the total global population, up from 34% in 1960, and continues to grow.” Interestingly, WHO notes that the growth is concentrated in less developed regions of the world. For that reason, the May 20, 2016 edition of the journal Science was dedicated to our “Urban Planet.” The introduction to the special issue, titled “Cities are the Future,” describes the impact of global urbanization. “The implications are sobering. The land area needed to provide city residents with food, energy, and materials is expanding; this ecological footprint is often 200 times greater than the area of a city itself. The resulting carbon emissions, added to those from cities themselves, mean that urbanization is now the main driver of climate change.” A “perspective” in Science’s blowout issue, written by Terry Hartig and Peter H. Kahn, Jr., and titled “Living in Cities, Naturally,” addresses some of the physical and psychological malaise that urban residents can experience when they are disconnected from the natural world. They also discuss an impact of urbanization that may be more subtle but far-reaching. When city dwellers are divorced from nature and a sense of the richness of the natural world, they start to normalize environmental degradation in what Hartig and Kahn call “environmental generational amnesia.” “[P]eople do not feel the urgency or magnitude of problems because the experiential baseline has shifted.” In other words, to paraphrase Donald Rumsfeld, urban dwellers don’t know what they don’t know about environmental change. They have no real reference point. They can only measure changes to their natural environment based on vague memories of childhood experiences. “Providing opportunities for people to experience more robust, healthy, and even wilder forms of nature in cities offers an important solution to this collective loss of memory and can counter the shifting baseline,” Hartig and Kahn write. L.A. Can Lead the Way Greg Pauly, curator of herpetology and co-director of NHMLA’s Urban Nature Research Center (UNRC), grew up in a suburban neighborhood near San Jose, California. He spent his afternoons wandering the nearby hills searching for lizards. He also rescued and rehabilitated a menagerie of three-legged, no-tailed lizards that had been maimed by neighborhood cats. His early relationship with these lizards, and the acute awareness of the natural and unnatural environments which they navigated, spurred his desire to study and protect them. “When my father was growing up in Pasadena, horned lizards were a common part of the landscape. That species is now entirely gone from the L.A. basin. At the UNRC, we’re trying to understand how species have responded to urbanization and how their distributions are changing.”
Once common, the majestic horned lizard is no longer found in the L.A. Basin. Argentine ants have displaced native ant species on which the horned lizard feeds. The well-camouflaged lizard above was recently photographed in Kern County. Photo by: Martin Schlageter “Los Angeles is a biodiversity hotspot,” says UNRC co-director Brian Brown. “It’s an area of great diversity, but it is also under great threat. Through collaborations and access to scientific resources, UNRC is creating the world’s largest urban biodiversity survey. Our research can help inform urban planning policies to minimize impacts on native species.” We are well past the era of boosters selling the young L.A. as a utopia of unbridled innovation, opportunity and wellness. And we are also beyond the bleak, Blade Runner-esque dystopian vision of L.A. that dominated in the latter half of the past century. Like all cities, Los Angeles, even at its urban core, remains a dynamic, living ecosystem. Understanding, protecting and promoting the region’s biodiversity is our next frontier. If you’d like to be involved in efforts to document and protect L.A.’s biodiversity, check out our Citizen Science program. Or you can donate to the UNRC.
July 26, 2016
The author, Emily Hartop, investigating a phytotelma formed by exposed tree roots. Photo by Brian Brown. One of the many benefits of doing research in urban environments is the ability to spend a day in "the field" by simply walking out your door. Brian Brown (Curator of Entomology at NHMLA) and I did just that on a recent morning, and found ourselves investigating some unexpected phytotelmata in the exposed roots of large Ficus trees growing in front of the Exposition Park Rose Garden next door to the NHMLA. Phytotelma (plural phytotelmata) is a fancy word that translates as "plant pond" and refers to any captured water environments created by plants. Some plants have evolved specifically for this purpose, like carnivorous pitcher plants . Other phytotelmata are quite accidental, such as holes in logs or trees, bamboo internodes, or leaves or flowers that capture water. These ponds are often host to many types of immature aquatic insects, and can be teeming with life. The small ponds we found in the Ficus roots were no exception.
Immature mosquitoes thrive in murky phytotelmata! Photo by Brian Brown. The first thing we noticed in these phytotelmata were hundreds and hundreds of mosquito larvae (photo above). Although the first pond we explored (pictured at top) was shallow and less than two feet long by eight inches wide, it easily contained several hundred mosquito larvae (detail photo of a larva below). This reinforced an important lesson about captured water: the smallest environment can breed incredible numbers of insects! This is why checking for standing water in potted plants, and overturning buckets so they don't collect water is so important. A container left carelessly in the backyard that collects a bit of sprinkler water can, within just a few days, turn into a house full of mosquitoes.
A mosquito larva displayed on a leaf. Photo by Brian Brown. Although there were a number of aquatic maggots that we observed, many of them we will need to collect and rear to adulthood to identify. We did find one real beauty that is instantly recognizable, however! Eristalinus taeniops, an introduced flower fly whose larvae are commonly called "rat-tailed maggots" (see photo below) were buzzing around a particularly stagnant (and stinky!) phytotelma we investigated. It wasn't long before I spotted one of the large, squishy maggots in the putrid water, and thrust my hand into the rotting water! For science! The maggot is pictured below (my hands still smell)!
A rat-tailed maggot pulled from the stinky depths! Photo by Brian Brown. Rat-tailed maggots are able to live in the smelliest, most stagnant of waters because of their breathing tube "tail". Although their beginnings are stinky and they aren't the most attractive of maggots (although I think they're adorable), as adults they are known as Stripe-eyed flower flies and they are the most gorgeous, impressive honey bee mimics you might ever see (photo below).
A stripe-eyed flower fly resting on a tree root near the phytotelma where we found rat-tailed maggots. Photo by Brian Brown. This species was previously found in the NHMLA Nature Gardens, but attempts to locate the larvae nearby had been unsucessful. Perhaps these beauties have been developing in the phytotelmata next door for years! It was an amazing morning that exposed a miniature world so close by, but unexplored. It was a great example of what makes urban environments so exciting: they are constantly changing and full of unexpected surprises!
July 19, 2016
Allison (Allie) Balthazor, a Gallery Interpreter at NHMLA, recently had a new family move in next to her apartment. Instead of a U-Haul, all they brought were a few sticks and twigs. Allie lives in an apartment complex in Burbank and not off the grid in a local wilderness, so of course her new neighbors were not humans. They were a mated pair of Mourning Doves (Zenaida macroura)! Footage of female Mourning Dove guarding her nestling in the nest, seemingly unfazed by the urban sirens passing by. Video by Allison Balthazor.
Twigs and branches being set up by Allison’s new neighbor. Photo by Allison Balthazor. Allie shares her entertaining story with us: “The property manager was not happy about them moving in, and he wanted to kick them out. (Maybe it was because they didn’t sign a lease!) Of all the pest problems you can experience in an apartment, I’d much rather live with a Mourning Dove family than with bed bugs ANY DAY! The doves first brought some twigs with them and stuffed them in the case above the fire extinguisher, then they formed them onto a little twig wreath. Shortly after, I saw one egg appear. The next day, when I came back from work, there was a second egg. The parents took turns incubating the eggs, and the chicks hatched, grew and fledged surprisingly quickly. The property manager was happy when they left. But his glee was premature. They returned not two weeks later, built another nest, and are raising a second family.”
Nesting on fire extinguisher at eye level at a semi-indoor hallway. Photo by Allison Balthazor. Kimball Garrett, NHMLA’s ornithology collections manager, says that Allie’s observations are consistent with known Mourning Dove breeding patterns. They only need approximately 30 days between the initiation of the first and second clutches of eggs, and can actually lay new eggs while the first brood of offspring are still being tended. Which is why Mourning Doves are one of the most abundant species in the United States, with a population of 350 million. Human parents, or soon-to-be parents, may be able to learn from these avian team players. The male and female doves work together to make sure their breeding is a success. The male chooses the territory, the mom finds the actual nest site, and the male gathers branches and twigs for the female to construct the nest. Both parents produce crop milk—a highly nutritious secretion from the lining of the doves’ crops—and they consume snails and bone fragments to aid in the production of the delicious baby bird formula. Unlike the ubiquitous Rock Pigeon (or Rock Dove—otherwise known, and loathed, as our common domestic pigeon) that was introduced from Europe into North America in the early 1600s, Mourning Doves are a native dove species in Los Angeles. Pigeons and doves are part of the same taxonomic family (Columbidae). Species known as “pigeons” typically have a heavier build with shorter necks, and broader, more squared-off tails than doves. Interestingly, Mourning Doves are more common than Rock Pigeons inside the NHMLA Nature Gardens, though there are more Rock Pigeons in the surrounding buildings and open lawns.
Mourning Dove nesting in the NHMLA Nature Gardens. Photo by Allison Balthazor. Doves and pigeons are the only birds, other than sandgrouse, that have the unique ability to suck and swallow water without lifting their heads. This may be an anti-predator defense, as they are ground-feeders and need to stay extra-vigilant. Mourning Doves are typically recognized as the lighter colored and pointy-tailed pigeons with wings that whistle in flight. They are often confused with owls due to their cooing “hoo-OOOoo, hoo, hoo-hoo” call. The only other common native Columbidae family member in the L.A. Basin is the Band-tailed Pigeon. Its distribution is centered in the foothills and forests, although many have colonized the suburbs and even downtown L.A. The native Mourning Dove, however, is possibly the most widespread bird in Southern California, which is impressive given how many bird species occupy the region. A few non-natives are becoming increasingly populous. Introduced species that thrive in a new region are usually generalists (flexible diet, habitat preferences, and behavior). Those characteristics allow them to outcompete less flexible native species that have overlapping ranges and habits. Similar to the Mourning Dove, the Eurasian collared dove is an introduced species that has become widespread. One of the easy ways to distinguish between the two species is by looking for the distinctive black collar on the back of the collared dove’s neck. They are also stockier and much paler than Mourning Doves. Eurasian collared doves were accidentally released in the Bahamas in the 1970s and subsequently spread to Florida. Throughout the 1990s and into the early 2000s they spread rapidly across North America, including California. A separate introduction of collared-doves took place in Ventura in the early 1990s (Garrett et al. 2012).
Eurasian collared dove documented on iNaturalist by @nhmordenana. Perhaps, one of the reasons dove species do better in our region is because they aren’t hunted. Mourning Doves are a highly hunted game bird in North America, but L.A. doesn’t have a robust hunting culture, nor is hunting even allowed within city limits. You can now appreciate our common Mourning Dove wherever you go in L.A. If you see a dove, take a moment to appreciate its quirkiness, try to ID it, and send a photo to our L.A. Nature Map. References: Garrett, K. L., J. L. Dunn, and B. E. Small. 2012. Birds of Southern California. R. W. Morse Company, Olympia, Washington. p. 219. Mirarchi, R. E. and T. S. Baskett. 1994. The Mourning Dove (Zenaida macroura). In The Birds of North America, No. 117 (A. Poole and F. Gill, Eds.). Philadelphia: The Academy of Natural Sciences; Washington, D.C.: The American Ornithologists’ Union.
July 12, 2016
Jesse Brewer Park. Useful, if not exactly lovely. Photo by: Brian Brown Across a small lane from the Museum lies Jesse Brewer Park, a modest, if thirsty, area of lawn, trees and playground equipment. Usually, there are homeless people encamped there, waking up in the morning as I arrive at work. I sometimes look at the park and think that it is an uninspired space compared to the Museum’s Nature Gardens, but it is surely better than concrete, providing much-needed play space for kids. But what, I ask myself, does it provide for wildlife? Surely there must be some habitat, since the park has large, mature trees. Recently I walked across the road with camera in hand to see if I could find something interesting. It didn’t take long. The sycamore trees along the east side are dotted with pupae of ladybird beetles, or ladybugs. Like all beetles, ladybugs have “complete” metamorphosis, with an egg, larva, pupa, and adult stage. There are no “baby” beetles that somehow grow into larger beetles; once an adult emerges from its pupa, it is done growing.
Yes, this is a beloved creature: ladybug pupa. Photo by: Brian Brown
Looking like some fabulously ornate shell, a ladybug pupal skin nested inside its bristly larval skin. Photo by: Brian Brown I found a number of pupae decorating the trees, usually skirted with their spiky larval skins. Some of them looked a little different and might represent other species. Finally, I came across an adult, a still-pale-colored (from having just recently emerged) Harmonia axydris, the Halloween ladybug, so named by my friend John Acorn because of its orange color. It is an introduced species that has caused concern that it might be competitively excluding some native ladybugs, but in Jesse Brewer Park they are a welcome decoration on the sycamore trees.
Harmonia axydris, the Halloween ladybug. Photo by: Brian Brown Find nature in your local park? Share your photos with us, so they can become data points for science. Use #NatureinLA to share on social media, or e-mail your observations to firstname.lastname@example.org, or upload them directly to iNaturalist using the free app.
July 5, 2016
Have you ever wondered what the inside of a snail's mouth looks like? The anatomy involved in land snail and slug feeding is fascinating. Well, I’d like to guess that it is more fascinating than you’d expect, if you’ve ever thought about snail and slug feeding in the first place. Snails and slugs have evolved to eat just about everything; they are herbivorous, carnivorous, omnivorous, and detritivorous (eating decaying waste from plants and other animals). There are specialist and generalist species that eat worms, vegetation, rotting vegetation, animal waste, fungus, and other snails.
Brazilian snail eating lettuce. Thousands of Microsopic Teeth! Snails and slugs eat with a jaw and a flexible band of thousands of microscopic teeth, called a radula. The radula scrapes up, or rasps, food particles and the jaw cuts off larger pieces of food, like a leaf, to be rasped by the radula. To understand what the single jaw and radular band look like in a terrestrial snail, two Museum interns (from Glendale Community College), Ala Babakhanians and Richard Laguna, photographed a common European Garden Snail (Cornu aspersum) eating a film of cornstarch and water on a piece of glass. This clever method was inspired by the Snail's Tales blog.
Underside of Cornu aspersum showing the single reddish-brown jaw of the mouth.
Close up of the open mouth of Cornu aspersum showing the jaw and the pale-colored ribbon of teeth called the radula. A Close Look at a Slug's Rasping Radula The only way to truly appreciate the microscopic teeth of the radula is to look at them under a microscope. To do this, Ole Willadsen, another Glendale Community College intern at NHMLA, dissected out the radula from a non-native slug found on Sunset Boulevard.
Limacus sp., non-native slug found in Los Angeles by Cedric Lee. The radula was imaged using the Museum's scanning electron microscope (SEM), which creates an extremely detailed and highly magnified picture of the specimen examined.
SEM image of central radular teeth Limacus sp. specimen shown above.
SEM image of marginal radular teeth Limacus sp. The fascinating feeding anatomy of snails and slugs is also helpful in determining their species identity, if and when that is in question. Since we sometimes don’t know the identity of non-native species we encounter in Los Angeles, the size and shape of their single jaw and thousands of radular teeth can be as informative as they are beautiful. **Can you hear a snail eating? Yes! Check out Elisabeth Tova Bailey’s book The Sound of a Wild Snail Eating. If you’d like to be involved in efforts to document and protect L.A.’s biodiversity, check out our Citizen Science program. Or you can donate to the Urban Nature Research Center.
June 28, 2016
The following is a sneak peek at @NHMLA's upcoming L.A. Nature Guide. This is one of 100 species accounts that will be in the book: Stink beetles can be seen bumbling across almost any hiking trail in our local mountains and other natural areas. Hikers in Griffith Park often spot them. What are they doing? Since they can not fly—their shield-like front wings are fused together—they have to walk everywhere. Scientists have followed them and found out they are usually in search of food. They are so good at living in dry climates, they can get all the water they need from the plants they eat.
Stink beetle wanders across a dry wash in Lytle Creek, California. Photo taken by Lila Higgins. Chemical Defense = Not Dinner If a stink beetle is disturbed, it has a few ways to escape trouble. Some species freeze and play dead—laying on their backs with all six legs stuck in the air. There is another strategy that is a bit more aggressive: The beetle will turn its back to the danger, and raise its rear end into the air. Though this sort of defensive posture might be threatening to some creatures, an animal like a hungry coyote may need further incentive to back off. The stink beetle ejects a dark brown, unpleasant smelling substance from the tip of the abdomen—the would-be predator will not make a meal of something so foul tasting. Stink beetle stink is made of a chemicals called quinones, which are also found in photographic developing agent. Disable the Stink, Eat a Meal Some animals have figured out how to deal with the stink. Skunks grab the beetles and roll them on the ground until they expel all of the chemicals. Grasshopper mice, take the beetles and stick their hind ends in the sand. The mouse then delivers a deathblow to the head, and then can safely eat its prey. A Grub’s Life Larval (immature) stink beetles are known as mealworms—similar to those that pet owners purchase to feed their lizards, and also a favorite for many local lizard species. They are heavily armored grubs that live their entire larval stage underground. Very little is known about their habits—they feed on plant material and fungi and rarely come to the surface. **Thanks to Museum entomologists Brian Brown and Emily Hartop for their help in writing this and all the other insect accounts for the L.A. Nature Guide.
June 22, 2016
What’s that smell?! It’s baby skunk season! Mother striped skunks (Mephitis mephitis) are on high alert and especially territorial between mid-May and mid-June because they are protecting their kits (another, more adorable word for baby skunks). After all, their scientific name, Mephitis, is Latin for "bad odor" and also the name of the Roman goddess of noxious vapors (a.k.a. bad gas) and illness, which makes sense since most people and animals don’t feel their best after getting sprayed, especially in the face and eyes.
Mephitis mephitis, was the odor so bad they had to name it twice? Usually you know you have a striped skunk living in your neighborhood long before you ever see one, thanks to their pungent spray. However, a striped skunk recently showed up on our camera trap without first indicating its malodorous presence to the NHMLA Nature Gardens staff. The skunk was photographed three times in March. It is the 11th mammal we have recorded in the Nature Gardens (if we include humans, it's number 12), and had never been detected by our staff or camera traps until now. In fact, according to the Museum's mammal collection department, it is the first striped skunk EVER documented in Exposition Park!
If you live in Los Angeles, you most likely live in striped skunk territory. You are also likely aware of your smelly neighbors thanks to the spray left behind after they are run over by a car or startled in the middle of the night. They were not only in Los Angeles during the Ice Age, but they were already widespread throughout the region by then. Beyond Los Angeles, the striped skunk’s range extends across most of North America and is one of twelve skunk species in the world, mostly limited to the Americas. (Except for stink badgers, which live in Borneo, Sumatra, and the Philippines.) Although they are familiar, urban-adapted mammals, they adapt to the city differently from other predators similar in size and diet, such as raccoons and opossums. Did you know L.A. County is home to two skunk species? Western spotted skunks (Spilogale gracilis) also share the Southland with the more popular striped skunks, but in much fewer numbers. The photo below, taken in Altadena, is remarkable because a spotted skunk has not been documented in the nearby Pasadena area since 1920.
Like raccoons and opossums, skunks are omnivorous and capable of eating just about anything, but they seem to favor insects. Their long, curved claws make them excellent, and sometimes destructive, lawn specialists. They dig up lawns in search of grubs, but are also willing to consume leftover pet food, fallen fruit, garbage, and other anthropogenic leftovers. They are solitary and territorial but will participate in communal feeding with other species (even predators!) as long as they are given a small buffer around their meal. A study in Chicago revealed that skunks did not alter their feeding habits in areas with concentrated human food resources and preferred to forage in open grass when available (Gehrt 2004). In other words, they retained their insect-feeding behavior in grassy habitat when possible. Striped skunks also require ground-level or subterranean denning habitat in order to survive in the city. Like most L.A. mammals (except squirrels), skunks are nocturnal, allowing them to roam the streets and nearby hillsides unnoticed. They adapt to urbanization by denning in forested or grassy habitat along the edge of the city, in vacant lots, under buildings like one of the Dodger Stadium dugouts, or even sometimes partially above ground. For instance, researchers from NHMLA were on their way to conduct a reptile and amphibian survey along the L.A. River and discovered a shallow skunk den with kits within a crack in the asphalt along the L.A. River. Inside were some adorable kits.
We often wonder how these wobbly walkers with small statures hold their own against humans and bigger competitors. Research has shown that predators as large as pumas respond to the characteristic black and white coloration by avoiding skunks unless they are desperate for food. However, predators seem to display stronger avoidance following a negative interaction. Skunks will most often run away if they feel threatened, but when they feel cornered they will arch their backs, stare down their target, raise their tails, and spray their very pungent musk—called butylmercaptan and containing sulfuric acid—at the victim. They can accurately spray up to 16.5 feet (5 m), usually directed toward a predator’s eyes, which can cause temporary blindness. Like many Angelenos, I have first-hand experience. Because I grew up just outside of Griffith Park, skunks were common in my neighborhood. My dogs were repeatedly sprayed. Recently, a territorial and smelly mating pair turned the crawl space beneath my apartment complex into a love shack and had to be evicted using bright lights and a one-way door.
A more memorable moment was when I was in high school and I awoke to the familiar scent of a skunk. It was especially strong because my bedroom window was open and the dead skunk had been run over directly in front of my family’s home. I continued to get ready for school, and my nose eventually got so used to the smell that I didn’t notice it anymore. I arrived to class, feeling sharp in one of my favorite jackets, and as class began I heard murmuring and realized my classmates were complaining about a smell. One kid hissed, "What is that smell?!" Another kid shrieked, "It smells like skunk!” At first I was confused because I couldn’t smell it, and then I was mortified—the smell was coming from me! There were good-looking girls in the class so I didn’t want to own up to being the source of the stench. I did what many teenagers do; I pretended it wasn't me. I then smoothly asked to use the restroom and ran to my locker to dump the jacket. Nobody ever found out, and I've never told anyone until now! The jacket and all the other clothes in my closet took about a week to stop smelling.
Whether we like it or not, skunk essence and associated stories go hand in hand with the natural history and ecology of L.A. Although smelly, skunks have an important role as predators of insect pests. Unfortunately, there is very little research done on urban skunks so we don’t clearly understand all their responses to urbanization. It is evident, however, that they do not alter their behavior as intensely as other similar species in urban areas. All we know is that they are limited by access to den sites. Until more research is done, striped skunk population declines or spikes will go unnoticed. We may never know how Angelenos and other city dwellers can better coexist with striped skunks without more baseline information from urban areas. Meanwhile, citizen scientists (especially nocturnal citizen scientists) can get the ball rolling by sending in photos to the L.A. Nature Map. Please keep your eyes and noses on high alert and send us your photos of neighborhood skunks while you’re out and about at night. And keep a safe distance, of course! References Elbroch, M. and Rinehart, K. 2011. Peterson Reference Guides to Behavior of North American Mammals. Houghton Mifflin Harcourt Publishing Company, New York, New York. pp. 187-192. Gehrt, S.D. 2004. Ecology and management of striped skunks, raccoons, and coyotes in urban landscapes. In Predators and People: From Conflict to Conservation (N. Fascione, A. Delach, and M. Smith, eds.) Island Press, Washington, D.C. pp. 81-104. Rosatte et al. 2010. Striped skunks and allies (Mephitis spp.). In: Urban Carnivores: Ecology, Conflict, and Conservation (Gehrt, S.D., Riley, S.P.D., Cypher, B.L., eds.). John Hopkins University Press. pp. 97-105.
June 14, 2016
Just in time for summer, baby Arroyo chub have hatched in our Nature Garden pond! Sharp-eyed Will Hausler from live animal programs spotted dozens of tiny black fish darting around in the shallows at one end of the pond. He shared his discovery with Leslie Gordon, our live animal programs manager, who arranged the chub introduction and has been keeping tabs on them.
The tiny chub in the pond (left) and darting out of the photo (right). Chub have a black stripe on the side which is very obvious in the juveniles. Photo credit: Will Hausler, Chris Thacker. Her first thought was that they must be the offspring of the chub we released in March, but she wasn’t sure. It’s hard to tell what kind of fish you’re looking at when you only see it from above, especially if it’s tiny and fast. So I got to pull out my aquarium nets and go do some field work just steps from my office! The little guys were indeed zippy, but I captured one and confirmed the identification: definitely baby Arroyo chub (Gila orcutti). The adult chub are very elusive and rarely seen, and we were unsure whether or not they liked their new home. Confirmation that they are breeding is very good news, because it means they are thriving and have found places to spawn in the vegetation. Arroyo chub are a kind of minnow, and they are one of Los Angeles’ few native freshwater fishes. They only live here in Southern California, where they are classified as threatened. Urbanization has reduced Arroyo chub populations in the Los Angeles, San Gabriel, and Santa Ana rivers, where they were once common. The amazing thing about chub is how well-adapted they are to our natural cycle of hot, dry summers and occasional floods in rainy winters. Before the rivers were channelized with concrete, they would overflow their banks in years of heavy rain, and spread in wide puddles across the flatlands. These intermittent floods were a fantastic opportunity for Arroyo chub, allowing them to move between our rivers and creeks, mix, and even found new populations. For a fish, dispersing like that is a big gamble, and chub are experts at it because they can tolerate tough conditions like wide variations in water temperature and low oxygen levels. They will eat any tiny thing they can get, mostly insects and algae. They are also great at controlling mosquitos by eating their larvae, which is why we brought them into our pond in the first place.
Preserved Arroyo chub from our Ichthyology collection. They still have the black stripe on the side, but it's not as distinct. Photo credit: Chris Thacker. The ways that animals move and invade new habitats are things we think about a lot here at the Museum. We study many species of lizards, frogs, snails, spiders, squirrels and insects that have come from somewhere else and made a home in Los Angeles. These new arrivals have to contend with different environments, food, and predators than they are used to, and many don’t survive. The ones that do tend to be generalists, easygoing about tolerating various environments and the food and conditions they find there. Our chub are natives here, but they share those same characteristics, making them tough invaders and good adapters to new habitats. When they get to a new place, they can quickly reproduce and increase their numbers, which is exactly what they’ve done in our Nature Garden.
June 2, 2016
In the entomological world, “scavenger” can be a dismissive term, hurled at animals that seem to feed indiscriminately on any available garbage or rotting material. The ultimate scavengers are indeed those insects that frequent trash bins and dumpsters: unsophisticated diners on our scraps and leftovers, annoying infesters of our cities and houses. The image of an unsavory “scavenger” can obscure some fascinating and extremely specific matters of lifestyle that defy the notion of a creature with wholly undiscerning habits. One example is our previously featured “coffin fly” (Conicera tibialis), a tiny phorid that burrows through the soil to reach its buried prize. This fly is perfectly capable of going through its life cycle in test tubes, feeding on meat, but in nature it is virtually never found in an unburied corpse. I was reminded about scavengers by the submission to the Museum of some fly pupae, found in the shells of dead snails by SLIME participant Cedric Lee. We reared the pupae to adulthood, and each one yielded an adult sarcophagid fly. The flies of this family (Sarcophagidae; often shortened to “sarcs” by dipterists—i.e., fly specialists) are commonly called “flesh flies” due to their breeding in dead bodies and attraction to nearly all types of noxious decaying material: carrion, dung, dead insects, etc. They are large flies, with gray and black striped bodies and red eyes. The fact that, at least externally to a non-expert, most sarcs look extremely similar leads to their often being labeled as “just” scavengers. In fact, sarcs are among the most diverse families of flies when it comes to the types of lifestyle they employ. The larvae of various species are: scavengers (often highly specialized), predators (that feed on and kill more than one host), parasitoids (that feed on and kill a single host), and true parasites (that feed on but do not kill a host). Unfortunately, for me, sarcs are also among the most disgusting flies. I know my colleagues who work on sarcs—and who are as fond of them as I am of phorid flies—might be dismayed by my contempt, but I can’t help being revolted by their reproductive process. Sarcs are ovoviviparous, meaning that the eggs hatch within the female abdomen and the female deposits larvae, rather than eggs, on the food source. When studying phorids associated with millipedes, I have frequently been repulsed by the arrival of female sarcs, who immediately spew several maggots on the scene, ruining my experiments. The larvae enthusiastically crawl into the millipede body and start feeding. Of course, the most gut-churning sarcs are the parasites, some of which infest incapacitated humans and cause noteworthy and alarming medical conditions. Most people interact with sarcs soon after noticing the smell of something dead under their house or in the walls. They’ll start to see large, clunky sarcs flying around their windows, trying to escape the house. These flies are the offspring of a female who somehow found a way to lay larvae on or close to whatever died, and who have helped to get rid of the body. I am often asked by homeowners how to eliminate these flies, and my answer is to let them do their scavenging, so that in a few days all the decaying material will be gone. Circling back to my original point, Cedric’s flies are not just scavengers—they are probably highly specialized feeders on dead molluscs (several sarcs are known to do this). I say “probably” because it takes a specialist to identify sarcs, and we will have to send ours out to one of the three or four people in the world qualified to tell us what they are. Such unusual natural history discoveries can depend on the thoughtful observance of Citizen Science participants like Cedric. One of our top citizen scientists, Cedric will likely contribute to one of the first records of a species breeding in dead snails!
May 31, 2016
Metallic sweat bee (Agapostemon texanus) (Left) and Mason bee (Osmia sp.) (Right). Photo credit: Kelsey Bailey Backyards are not what they used to be. As an urban biologist who has spent countless hours exploring yards in L.A., I have seen lawns and rose gardens replaced by succulents and sages, bug zappers exchanged for hummingbird feeders, and swing sets coupled with bee hotels. More and more Angelenos are seeing their personal green space as not just a place to rest and play, but as integral habitat to share with local wildlife. Our Museum’s Nature Gardens are living proof that even in the core of the city, planting with purpose can have a profound beneficial effect. The area that was predominantly a concrete parking lot less than ten years ago is now home to 10 mammal species, 168 bird species, and heaps of insect species that we are continually discovering.
Sample of insects collected in mid-May of 2010 during the construction of the Gardens, next to sample collected in mid-May of this year. What a huge difference! Photo credit: Kelsey Bailey One group we are diligently observing are the bees. Los Angeles boasts over 500 (yes, FIVE HUNDRED) species of bees. The European honey bee gets most of the media exposure, but other bees are in need of our attention as well. Having created a pollinator-friendly Nature Garden through the careful selection of host plants and the provision of proper nesting areas, we can now document 15 species of bees that make the garden their home! The majority of these bees nest underground, so patches of bare dry soil are crucial for their survival. Others are cavity nesters, meaning they will use hollowed-out twigs or make use of holes drilled into wood, also known as bee hotels. Buckwheat, poppies, mallows and sunflowers are but a few of the flowers that we provide as essential food for these beautiful pollinators.
Leafcutter bees (Megachile sp.) in a bee hotel (Left) and Sunflower bee (Diadasia sp.) collecting pollen on mallow (Right). Photo credit: Brian Brown Many of our garden’s bees fly under the visual radar of the casual observer due to their small size. Small carpenter bees, mining bees and sweat bees are only a few millimeters, but they are just as important for pollinating flowers as their larger counterparts.
Mining bee (Perdita sp.) (left) and Small carpenter bee (Ceratina sp.) (Right). Photo credit: Kelsey Bailey Our most commonly collected and observed bees in the Nature Gardens are European honey bees and sweat bees in the Subgenus Dialictus. Many people are aware of the issues facing populations of honey bees that are raised and kept in captivity, but do not realize that feral (the bees that have escaped from captivity) honey bee numbers are quite high, often greatly outnumbering all other species of bees in our L.A. area insect surveys.
European honey bee (Apis mellifera) (Left) and Sweat bee (Dialictus sp.) (Right). Photo credit: Kelsey Bailey Expanding your sense of what bees do and how they appear (going “beyond the honey bee”), will open your eyes to a whole hidden world of beauty. Some bees glisten like shiny blue and green jewels, while others are completely fuzzy, adorable teddy bears with wings. Now that spring has arrived, we will be peeking inside flowers, checking our bee hotel and looking through our insect trap to see if we can add to our impressive list of bee species that call the Nature Gardens their home.
Mining Bee (Anthophora sp.) (Left) and Bumble bee (Bombus sp.) (Right). Resources Nests for Native Bees Pollinator-Friendly Plant List for California