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.
March 26, 2016
Pond life in motion. Video by Kelsey Bailey.
When we planned the Nature Gardens, there was never really any doubt that we would include a pond. Water sources are highly attractive to wildlife, so even while the concrete was being scraped off the work site, we began to imagine the creatures that might use ours. We were particularly interested to see what types of microscopic animals might arrive, as when they are properly displayed (and magnified), they present to the public a stunning and unfamiliar fauna.
In 2012 the pond was established as an essentially barren pool of rock with a few planters. Over the years the garden team has carefully added additional substrate on the bottom, more planters, and balanced the flow of the pumps and waterfall to make for quiet areas of micro habitats. What has grown is a pond that is rich with possibility for different groups of animals to utilize. The shallow shelf above the waterfall is an ideal place for yellow-rumped warblers to bathe and groom, and the faster moving water under the bridge are potential places for our native chub to hide and spawn. Like most urban habitats, however, the microscopic world of pond life has been little studied.
One chironomid larva eating another. Photo by Kelsey Bailey.
Recently, we took a sample of the debris gathered in the base of the plant by the dock, looking for those long imagined microscopic creatures. We found a lively community of strange, active animals that surprised even us with its diversity and beauty. The most easily visible are the snakelike immature stages (larvae) of non-biting midges of the family Chironomidae. Chironomid larvae are common in our pond, where they feed on algae, smaller organisms, or sometimes even each other! They attach their posterior end to a twig or root and wave around, looking for food in a mesmerizing, never-ending dance.
Also common in the pond are tiny crustaceans called ostracods, which look like animated seeds that scurry along the bottom, looking for food. Their patterned exterior is clamshell-like, with their many appendages extending between the “shells," propelling them rapidly through the water.
Water mite. Photo by Kelsey Bailey.
Unlike the ostracods that zoom around in the samples, the water mites are slow and tanklike in the water. They look like heavy-bodied spiders and they plod through the vegetation
Planarian flatworm. Photo by Kelsey Bailey.
Other, lightly less common creatures are the freshwater copepods, that dart through the water in jerky spurts, often carrying a pair of egg sacs behind them. We saw one planarian flatworm (though 2 ½ years ago, another staffer found one and wrote this blog about them), a comical looking animal that appears perpetually cross-eyed, a caddisfly larva with its case, and a few things that defy identification at this time.
Besides the photos displayed here, have a look at the accompanying video to get an idea of what this stuff looks like in real time. It’s an easy and fun way to get a look at an alien ecosystem that occurs on our own planet.
June 13, 2017
April 19, 2017
April 4, 2017
July 2, 2015
After three long years of planning, 45 arroyo chub were finally released into the Nature Garden's pond last week.
Arroyo chub (it's alive, don't worry!) held for a quick photo op before release into the pond! Photo by Richard Hayden.
Arroyo chub, Gila orcuttii, are a native freshwater minnow found only in the coastal streams of Southern California, says Chris Thacker, Museum Curator of Ichthyology (fishes). They are classified as threatened in this native range and are noticeably missing from the lower reaches of the Los Angeles river. So, when it came time to think about fish in the Nature Gardens pond, all our scientists and educators wanted Arroyo chub.
The chub were transported from the Riverside Corona Resource Conservation District in an extra large cooler. Photo by Jason Goldman.
Our philosophy about purposefully introducing animals into the Nature Gardens is pretty strict-we generally don't do it. However, we knew we were going to make an exception for fish in the pond. Why? Because, mosquitoes!
Although we're fascinated by all nature here at the Museum, we are definitely taking a stance against breeding mosquitoes in our pond. Which is a good thing, because the Greater Los Angeles County Vector Control District would step in and solve the problem for us if we didn't. Their solution would involve releasing 6-10 mosquitofish, Gambusia affinis, into our pond. But, we didn't want mosquitofish, we wanted a fish that was native to Los Angeles, something that could tell a better story about nature in L.A..
Arroyo chub have a great story.
According to Thacker, "these minnows were historically found in arroyos and rivers in Southern California, but are now only known from the upper reaches of our watersheds." This is true for the highly altered and concretized LA River, where the chub are noticeably absent. When Friends of the Los Angeles River studied the fish of the river in 2007, they found zero arroyo chub and 668 mosquitofish, more than any other sort of fish!
Although, these non-native fish are helping us to keep mosquito-borne disease cases down, they're also impacting other creatures that live in our rivers and streams. Museum herpetologist (reptiles and amphibians), Greg Pauly explains, "the name mosquitofish makes one think they are highly specialized on mosquitos, when in fact they are actually broad generalists and consume native amphibian eggs and non-target insects." The chub on the other hand are much more effective at eating mosquito larvae and predate less often on the frogs, toads, and native insects we are trying to encourage in our waterways. Because we wanted to encourage as much biological diversity as possible in our pond–especially all those dragonfly and damselfly nymphs–we pushed for chub.
So why don't vector control use chub instead of mosquitofish? There are a few reasons. Chub are much harder to rear in captivity than mosquitofish, and it's therefore easier for vector control facilities to keep up with demand. More importantly, as a native fish arroyo chub require permits from California Department of Fish and Wildlife for us to keep them. Interesting that no permits are needed for the non-native mosquitofish.
So, if you want to meet our new arroyo chub, come on down to the Museum. Thacker advises you to be patient, "They are skittish little fish and like quiet spots in the pond, so they will often be hiding, but can hopefully be spotted with a bit of dedicated observation."
September 12, 2012
Quick Dragonfly Update!
I've documented another dragonfly visiting our pond. It was a Black Saddlebags, Tramea lacerata. My phone's camera couldn't capture a picture of this fast-flying critter, but I was able to send myself an e-mail documenting the find. Here's the e-mail:
"Saw a saddlebags by pond
August 22, 2012
This brings our total number of dragonflies and damselflies to six species! Check out this recent post to see the the other five.
Black Saddlebags perching
Photo courtesy of JerryFriedman
May 17, 2012
Two weeks ago I told you I'd fill you in when I found dragonfly nymphs in our pond. I wasn't expecting to be able to give you this update so quickly, but SURPRISE, nature moves fast, people! In the last few weeks, I've found more than 50 dragonfly exuviae (the papery exoskeletons shed between molts) attached to the rocks of the pond. Of course, this prompted me to take out my dip net and look for nymphs in the water.Here's a picture of one I found:
Variegated Meadowhawk, Sympetrum corruptum, nymphFound May 5, 2012While I was dipping for the dragonfly nymphs, I found a lot of other macro-invertebrates. The list isn't very long, yet, but includes immature mosquitoes, chironomid midges, mayflies, and predacious diving beetles!
Mayfly nymph found May 5, 2012
Predacious diving beetle larva found in pondMay 4, 2012
I also found an adult predacious diving beetleonMay 5, 2012
May 10, 2012
On the tails (mammal and bird tails that is) of last week's post, I thought I'd continue to focus your attention on our wonderful new pond. Sam Easterson has set up some of his trusty camera traps next to the waterfall to see who might be visiting the pond. Check out the following images to see what he has found so far.
Nighttime is busy at the pond!
Stray cat...sorry, there aren't any fish in the pond yet
and no you can't eat them when there are!
Opossum...no tin foil in the pond either.
Although these night time endeavors are interesting, I think the action during the light of day is even more so. Over the last few weeks, Sam's traps have captured over 50 images of birds hanging out by the pond.
American Crow, Corvus brachyrhynchos
That is one good bath!
Black-headed Grosbeak, Pheucticus melanocephalus,
stops by for a moment.
Western Gull, Larus occidentalis, going in for a drink.
Camera shy Swainson's Thrush, Catharus ustulatus.
Male Western Tanager, Piranga ludoviciana
For the grand finale, watch three bird species drinking from the pond at once! We've got a Mourning Dove, Zenaida macroura, on the far left, a Western Kingbird, Tyrannus verticalis, center frame, and a Warbling Vireo, Vireo gilvus, doing a fly-by.
Want to see more creatures caught on camera trap? No problem, check out lots more pictures and videos on our flickr pool.
May 3, 2012
Last night I hosted an InSEX dinner at an undisclosed and secret location. No, we weren't eating insects (in fact, we had a lovely vegetarian meal). Instead, we were discussing their weird, wonderful, and various reproductive strategies!
Vietnamese Walking Stick, Baculum extradentatum
A great example of asexual reproduction
I also took some impressive beetles to show off
Here's an excerpt:
Sperm Wars-Unlike honeybees, dragonflies don't have exploding penises. Instead, they have an equally impressive mode of sperm competition. When a male dragonfly grabs a mate—clasping her roughly behind the head—he carries her away for a nuptial flight. After some brief struggling, the male bends his abdomen around and inserts his aedeagus (that's insect for penis) into her reproductive tract. With his impressively spiked member he scoops out the sperm left over from a previous mating, thus ensuring it is his sperm and no other's that will fertilize the eggs she is about to lay...
But how does this all relate to the North Campus and L.A.'s urban nature? Simple—we found our first dragonfly at the pond! According to Museum Ornithologist, Kimball Garrett (yes, he does dragonfly identification too), this is a male Variegated Meadowhawk, Sympetrum corruptum. He was sunning himself on a rock, possibly waiting for a female dragonfly to make an appearance. Unfortunately for him, none showed up while I was there.
Over the next few months, the pond will attract more and more adult dragonflies and, soon enough, we'll have them mating. In tandem, the coupled dragonflies will approach the water's surface and the female will lay her eggs. Unbeknownst to many, the immature form of dragonflies actually live underwater! After the eggs hatch, the dragonfly nymphs will find a cozy spot to hide in the reeds. It's a dangerous and murky life down there, I mean who would want to get eaten by a fish? One way that dragonflies can evade predators is through jet propulsion. They pull water into their rectal chamber and eject it at high speed, thereby propelling themselves in a forward direction, and hopefully out of harm's way.
When they're not trying to evade their own predators, dragonfly nymphs are voracious predators themselves! They have extendable mouthparts that can be "shot" out of their heads in less than three one-hundredths of a second. This is very fast indeed, and allows the nymphs to sit and wait until something comes within mouth's reach. As you can tell, dragonflies are much more than just pretty insects good for putting on greeting cards and tattooing onto various bodyparts. I mean, what other creature can you think of that has jaws of death, rectal propulsion, and a highly modified penis for sperm removal?
Male Variegated Meadowhawk basking in the sun
December 6, 2011
Piranhas are the stuff of B-movies, sensationalized nature television, and the tropical rainforest. Most would think they have little bearing on life here in L.A., however as I learned last week, this is not the case.
Taxidermied Red Piranha, Pygocentrus nattereri "lips" removed to accentuate teethPiranhas are here in L.A.! They are sometimes confiscated from pet stores and, on occasion, they are even found in our waterways. The Museum's Ichthyology collection houses over 30 confiscated piranha, and at least one that was caught in the "wild." According to the collections record, this Red Piranha (see below) was netted from "Simi Valley Public Golf Course, Lake B." It was collected on April 28, 1988 and measured 275mm (almost 10 1/2 inches)! Most interestingly the capture method box of the record states that that the "fish was in distress." I wonder if the piranha would ever have been discovered had it not been in distress? Before any of us decide to never go fishing for our wayward golf balls with our bare hands again, I have some happy news. Even in the Amazon basin, where Red Piranhas are native, humans are extremely unlikely to be injured by them, let alone die. The image of a school of piranha stripping all flesh from a whole cow or indeed a whole human, isn't much more than a sensationalized Hollywood gimmick (think James Bond's You Only Live Twice). This is because Red Piranha are actually scavengers preferring to eat dead, not living flesh. So next time you're fishing for your golf ball in the water trap, be safe in the knowledge that you're much more likely to get bitten by your neighbor's dog!
The Simi Valley Golf course piranhaOther piranha collected in L.A. come to the Museum directly from the California Department of Fish and Game (CDFG). CDFG staff often patrol pet stores and upon finding illegal creatures will confiscate them under California Law Title 14 Section 671. The fish are promptly brought to the Museum for identification and sometimes for permanent storage, though they may be taken briefly into a court of law as evidence! In May 2002, the Museum received 16 Red Piranha specimens confiscated from one pet store alone!
Red Piranha confiscated from pet storeI wonder if we'll ever find a piranha in the North Campus pond?
October 24, 2011
I went out for a walk around the North Campus today and this is what I saw:
They are filling the pond to make sure there aren't any leaks and that the waterfall cascade is level.
I went out for a walk around the North Campus today and this is what I saw:
They are filling the pond to make sure there aren't any leaks and that the waterfall cascade is level.
Underneath the pedestrian footbridge is the best spot for mushrooms. I think this is a morel, Morchella esculenta. I am consulting with some mushroom experts to see if they can make a positive identification.
Apparently the Monarch caterpillar I found two weeks ago made its pupal case on a wall. I just love how green they are!
June 9, 2011
This morning I got to work and did my usual cursory look out of the office window. This is what I saw:
Breaking ground on the pond I know a hole in the ground doesn't get many people excited, but it definitely made my day. Working with the North Campus design team, we spent many months designing a pond that could increase the biodiversity of the North Campus and be a fun and engaging place for visitors. The pond will be teeming with wildlife such as fish, freshwater invertebrates, visiting birds, and hopefully a colony of Western Pond Turtles, Actinemys marmota. Here is a rendering created by Mia Lehrer + Associates, so you can get a sense of what the pond might look like.
View of pond facing the Age of Mammals exhibit