We Californians are all under a state-wide mandate to stay at home, to minimize the spread of COVID-19 this spring. School hasn't been cancelled, but all classes have converted to distance learning. I had four days to figure out how to deal with that. Fortunately we are in spring break this week, which gives us all a little bit of a breather. I'm going to use the time to catch up on grading and plan for the second half of the semester.
The marine lab is also closed for business. Only essential personnel are allowed to be there. The term 'essential personnel' includes people whose responsibilities are animal husbandry. Since animals will die if I'm not there to feed them, I have met that criterion for essentiality. That's not a word, but you know what I mean. With so many fewer than usual people at the marine lab, there's a lot more wildlife activity. A few days ago I saw a long-tailed weasel (Mustela frenata) chase down and capture a young brush rabbit. I just barely had time to catch a quick shot with my phone.
The most noticeable thing, though, is the increased birdsong. The sparrows, finches, red-winged blackbirds, mallards, doves, towhees, and hawks are all making a lot of noise. The barn swallows (Hirundo rustica) returned to the lab on the 21st, right on time! Maybe this year they'll have a more successful nesting season than they did last year.
Yesterday I witnessed something I'd never seen before: a territorial dispute between a black phoebe (Sayornis nigricans) and a barn swallow. The fact that I had never seen it before in no way implies that it happens only rarely; maybe I've just never paid that much attention to these things before, or they've never happened while I've been around to watch.
Here's the story, in a series of snapshots.
Prologue. The barn swallow (H. rustica) is perched on one of the outdoor light fixtures. The phoebe (S. nigricans) swoops up from below.
The entire altercation lasted maybe as long as four seconds. I didn't see where the swallow flew. The phoebe remained on the rain gutter for about a minute or so, then took off over the meadow. Perhaps it has a nest somewhere nearby and was defending it. Both species build mud nests on cliffs and buildings, so these birds could be competing for nest sites. Or maybe phoebes just don't like swallows. Either way, this was the sort of interaction that I don't notice when there is a lot more human activity at the marine lab. Nature has a way of re-asserting herself when humans are removed from the scene for even a short period of time.
Back in 1994, the U.S. Army base at Fort Ord was closed in one of the base closure events that occur every once in a while. UC Santa Cruz (UCSC) acquired some 600 acres of the former base to establish the Fort Ord Natural Reserve, which serves as an outdoor laboratory and teaching space for students of all ages. University students from UCSC and California State University Monterey Bay (CSUMB) take classes and have internships on the Reserve. Kindergarten students visit the Reserve for what may well be their first experience of Nature. And I take my community college students there every year.
This year, Joe Miller, the reserve manager, had a lot of things for us to learn about, and we were kept busy all day. The first thing we did, after an introduction to the reserve, was hike to the first of several areas where Joe had set some rodent traps the night before.
They are live traps, baited to lure in a rodent. The doors shut on the rodent once it ventures inside to grab some seed.
There's a super high-tech method to getting a live rodent out of a trap without hurting either the rodent or the human. You hold the trap vertically, open the top end, slip a plastic bag over the open end, make sure there are no escape openings, then flip the trap over so the rodent falls into the bag. And voilà, instant mouse in a bag!
Then you work the rodent head-first into a corner of the bag with one hand, and reach into the bag and approach it from the back end. Follow the backbone forward, then grab the rodent by the scruff of the neck.
We caught three or four deermice, but the cutest rodent we saw was a pocket mouse (Chaetodipus californicus). Joe didn't bother with gloves because, as he said, these guys are really mellow. And it really was! He handed it to us and we took turns holding it.
I think it's called a pocket mouse because it's so cute you want to put it in your pocket and take it home.
We had to let the rodents go because Joe had other things for us to do. In addition to the rodent traps, Joe had set up pitfall arrays to catch herps (reptiles and amphibians). A pitfall array consists of two strips of aluminum flashing set up in the shape of a capital T. At each end of the T there is a pitfall trap. The critter runs or slithers along the flashing and then falls into the trap, which is a small bucket buried so the lip is just at ground level.
We got skunked on the pitfall traps--all of them were empty. We did, however, get to see herps. Joe showed us a couple of tiger salamanders, which he had permits to keep as teaching animals. These two animals are hybrids between the native tiger salamander (Ambystoma californiense) and a salamander that was introduced from Texas into California to be used as bait. As happened quite often, the bait species took hold in its new habitat and is proving to be a nuisance. In their larval stage they are voracious predators, gobbling up the larvae of other amphibians including those of endangered species such as the red-legged frog. In the area of FONR, pretty much all of the tiger salamanders are hybrids to some degree.
As with all other amphibians, tiger salamanders require a variety of habitats to complete their life cycle. They reproduce in water, and the larvae live in water. California has distinct wet and dry seasons, and the salamanders must find vernal pools where the water will last long enough for their larvae to metamorphose into the terrestrial adult form. Sometimes the pools don't persist long enough, and in very dry years the pools may not form at all. During the dry season, tiger salamanders may estivate underground, waiting until the weather gets cool and damp enough for them to emerge from burrows and forage on insects and small vertebrates.
One of the students had her heart set on seeing horned lizards, and her wish came true. Some UCSC interns working on the horned lizard mapping project caught a couple of small lizards for us to see. The larger adults aren't coming aboveground yet.
Like the tiger salamanders, the horned lizards face an uncertain future of their own. Their main prey are native ants. California has been invaded by Argentine ants--those are the little black ants that get into houses. The Argentine ants are extremely competitive and form supercolonies, wherein two or more adjacent colonies will merge underground and function as a single colony with multiple queens. They can and do outcompete the native ant species, and predators don't seem to like them. Unfortunately, the horned lizards don't eat the Argentine ants. If the lizards' food source is threatened by the ants, then the lizards could be in big trouble.
One of the things Joe wanted to show us was a plant with a tiny purple flower, that is just now starting to bloom.
This little plant, called greater yellowthroat gilia or sand gilia, is a California endemic species, found nowhere else. The State of California lists it as threatened, and the federal government lists it as endangered. It's a pretty plant, growing low to the ground because although it's March, we haven't had any rain for about eight weeks. And this is supposed to be our rainy season. Joe showed us some Gilia plantlets that were grown in greenhouses and had plenty of water, and they were three or four times as tall as the ones we saw in the field.
There is a lot of very interesting work going on at FONR these days, and it's exciting for me to see how many students are involved. Some of my students said they would contact Joe about internship opportunities, and I hope they do so. If I'm teaching Ecology again next spring, we're definitely coming back to Fort Ord, and I think we'll do an overnight camping trip. I'm sure the reserve is a completely different place once the sun goes down!
Of course, sea anemones don't have faces. They do have mouths, though, and since a mouth is usually part of a face, you can sort of imagine what I'm getting at. The sunburst anemone, Anthopleura sola, is one of my favorite intertidal animals to photograph. Of the four species of Anthopleura that we have on our coast, A. sola is the most variable, which is why it keeps catching my eye.
This afternoon I met the members of the Cabrillo College Natural History Club for the low tide at Natural Bridges. Here are some of the A. sola anemones we saw.
This past Fall semester the NHC went tidepooling at Pigeon Point. Today we were at Natural Bridges, and later in the spring we are going to Asilomar. I didn't intend it, but this school year the club is getting a look at three very different intertidal sites.
The first field trip of the semester for my Ecology class is always a jaunt up the coast to Rancho del Oso and Waddell Beach. It's a great place to start the practice of observing nature, because we can explore the forest in the morning, have lunch, and then wander along the beach in the afternoon. We really are lucky to have such a wide variety of habitats to study around here, which makes taking students out into the field really fun. My passion and expertise will always belong with the marine invertebrates, but it's good for me to work outside my comfort zone and immerse myself in habitats I don't already know very well. During this year's class trip to Waddell Beach I was struck by some things I had seen before but never paid much heed to. And also one very big thing that caught everybody's attention.
Depending on how much rain has fallen recently, Waddell Creek may or may not flow all the way into the ocean. Since California has a short rainy season, there are months when the creek is completely cut off from the ocean, due to both a lack of flow and the accumulation of sand on the beach. So far this rainy season, which began on 1 October 2019, we've gotten about 93% of our normal rain. However, we had a very wet December, and almost no rain since then. I wasn't sure whether or not Waddell would be flowing into the ocean. It was.
The students had many questions: What was he doing there? Was he sick? Was it a male? Was he dead? Well, no, he wasn't dead. And while I guessed from this view that it was a subadult male, I was secretly relieved to be proved right when we walked down the creek (keeping the mandated distance away from him) and looked back to see his big schnozz.
The elephant seal breeding season is coming to an end, but animals will continue to haul out and rest on the beach. This subadult male clearly isn't going to be dethroning any beachmasters this year, so he has taken the safe route and chosen a beach away from the breeding ground at Año Nuevo, which is ~2 miles up the coast. What I really liked about this particular animal was that we could see the tracks he made getting himself up the beach to the creek.
So that was the big thing. Eye-catching he certainly was, but to my mind not nearly as interesting as the small things we paid more attention to on the beach. It is tempting to think of sandy beaches as relatively lifeless places, compared to something like a rocky intertidal or a redwood forest. But for some reason, this trip I became intrigued by the dune vegetation. At first glance a sand dune seems to be a very inhospitable place for plants, and it is. Sand is unstable and moves around all the time, making it difficult for roots to hang on. Sand also doesn't hold water, so dune vegetation must be able to withstand very dry conditions. It's not surprising that dune plants have some of the same adaptations as desert plants.
I love this little sand verbena (Abronia latifolia)! It is native to the west coast of North America, from Santa Barbara County to the Canadian border. It is a sand stabilizer, decreasing the erosion that occurs. The sand verbenas also live in deserts; I saw them at Anza-Borrego and Joshua Tree last year. The beach sand verbena grows low to the ground, probably as a way to shelter from the winds that come screaming down the coast. Cute little plant, isn't it?
The other yellow beach plant we saw was the beach suncup (Camissoniopsis cheiranthifolia), a member of the primrose family.
Like the yellow sand verbena, the beach suncup is a California native. It grows along the entire coast, including the Channel Islands. Also like the yellow sand verbena, the suncup grows low to the ground. Its leaves are thick and a little waxy, to help the plant resist desiccation.
And now for the non-natives. I must admit, I had given very little thought to the plant life on my local beaches. I'd seen and studied beach wrack, but to be honest most of my attention is usually directed towards the water instead of up high on the beach where the plants live. This day I decided to photograph the plants.
This plant is a little succulent called European sea rocket (Cakile maritma). As the common name implies, its native habitat is dunes in Europe, northern Africa, and western Asia.
Cakile maritima has several life history traits that enable it to be carried around the world. It produces a lot of seeds, more so than the native dune plants. The seeds are dispersed by water and can be transported long distances in the ballast water of ships, which is probably how it got to California in the first place. It tolerates disturbances better than native dune vegetation, which allows it to be a superior competitor. Cakile maritima is considered to be invasive, meaning that it can survive and spread on its own in a non-native habitat, but its effects seem to be restricted to beach dunes. Despite its ability to thrive and outcompete our native beach plants, it appears to be unable to expand away from the sand.
Our surprise of the day was a beach mushroom! None of us had seen them before. This is Psathyrella ammophila, the beach brittlestem mushroom. Like sea rocket, it is also a European invasive. We were perplexed by this mushroom. Most of a fungus's body (mycelium) is underground. The mycelium spreads through soils as very thin threads called hyphae. Every once in a while the mycelium sends up a fruiting body, which is what we call a mushroom. There is no way to know, from the location of mushrooms, where and how far the mycelium spreads underground.
The presence of a mushroom on the beach means that a fungal mycelium is feeding on something in the sand. There isn't much plant matter buried on beaches, but we hypothesized that perhaps one of the logs from the forest had washed down the creek and been deposited on the beach. It would then be buried in sand, along with all the mycelium it carried, and a mushroom could have sprouted up through the sand.
Well, it was a good hypothesis.
I posted my photo to a mushroom ID page, and it was identified as Psathyrella ammophila. My submission to iNaturalist came back with the same result. A little research led me to another non-native invasive species, Ammophila arenaria, the European marram grass. Notice that the species epithet of the mushroom is the same as the genus name of the plant? That was my first clue. Marram grass is one of the most noxious weed species on the California coast. It was intentionally introduced to the beaches in the mid-1800s, to provide stability to the dunes. It is very good at that, but also spreads very rapidly, usually growing upwards away from the ocean. That said, marram grass also breaks off chunks that can survive in the ocean and float off to colonize new beaches.
The fungus Psathyrella ammophila grows as a saprobe on the decaying roots of Ammophila arenaria. No doubt the fungus was introduced along with the marram grass as an inadvertent hitchhiker. Since there is so much marram grass on our beaches, it's safe to assume that there is a lot of Psathyrella, too. That means it's time to start looking for mushrooms on the beach!
A while back now I went out on a low tide even though the actual low was after sunset. I figured that it was low enough that I'd have plenty of time to poke around as the tide was receding. And given that there were promising clouds in the sky, I took my good camera along just in case the sunset proved to be photo-worthy. Having had enough of crowds in the intertidal at Natural Bridges the previous day, I decided to venture up to Pistachio Beach, which isn't as heavily visited.
I ended up spending only 45 minutes in the intertidal, all the while watching the sun sink lower in the sky. It was already too dark to take many photos in the tidepools, but there were some interesting things on the beach.
The majority of shells that wash up on any beach are going to be molluscs, usually either gastropods or bivalves. I've often seen living red abalone (Haliotis rufescens) hidden in nooks and crannies at this site, so it's not surprising to find their shells on the sand. Usually, though, the shells are a little beat up. This one was intact, with a lovely layer of nacre inside.
This butterfly-shaped object is one of the shell plates of Cryptochiton stelleri, also known as the gumboot chiton. Cryptochiton is the largest of all chiton species; the largest one I've ever seen is the length of my forearm from elbow to fingertip. Like all chitons, C. stelleri has a row of eight shell plates running down the dorsal side of the body. Unlike other chitons, however, in Cryptochiton the plates are covered by a layer of tissue called the girdle and not visible from the outside. If you run your finger down the back you can feel the plates under the girdle. I never thought about it before now, but it seems that the name Cryptochiton refers to the hidden chiton-ness of the animal.
Anyway, Cryptochiton lives mostly in the subtidal, although you can occasionally see them in the very low intertidal. As subtidal creatures they have neither the ability nor the need to cling tightly to rocks, as their intertidal cousins do. This means that when big swells come through at low tide, they can get dislodged and wash ashore. I know from personal experience that the tissue of Cryptochiton is really tough. Once a pal and I were trudging back after working on a low tide and came across several dead Crytochiton scattered over the beach. We decided to do an impromptu dissection and try to salvage the plates, hacking away with her pocket knife. The smell was horrendous, and after several minutes we made practically zero progress, so we gave up. I've seen gulls pecking at dead Cryptochiton, too, and they didn't seem to have any success either. However, their bodies do eventually disintegrate, or something manages to eat them, and their naked plates can often be found on beaches.
I've never seen anything like this before. It's hard to tell from the photo, but these two rock faces converge into the crevice, sort of like the adjacent pages in an open book. This side of the rock surface faces away from the ocean and will never be subject to the main force of pounding waves. The barnacle in the middle is attached pretty much in the deepest part of the crevice, and is surrounded by mussels, which are then surrounded by limpets.
Now, all of these animals recruited to this location after spending some period of time, from a few days to a few weeks, in the plankton. The barnacle certainly can't move once it has settled and metamorphosed. Newly settled mussels have a limited ability to scoot around a bit but are generally stationary once they've extruded their byssal threads and fastened them to something hard. The limpets, on the other hand, are quite mobile. The barnacle and mussels gave up their ability to move around after they became benthic, but limpets can and do locomote quite a bit--in fact, they have to, in order to feed. So in a sense, these limpets "chose" to aggregate together long after settlement.
What are the ecological implications of this pattern?
Well, for one thing, that barnacle is a genetic dead end. I've written before about the bizarre sex lives of barnacles. This one lone barnacle, far from any others of its species, is not able to reproduce. It has nobody to copulate with. It is possible that other barnacles will recruit to the mussels (Pollicipes is often associated with Mytilus), but until then there will be no sexy times for this individual.
Another ecological consequence concerns the limpets. If these are owl limpets (Lottia gigantea), then some of them will grow up to be the big females that maintain farms on the rocks where they manage and harvest the crop of algal film that grows. These big females are territorial, and will bump or scrape off any creature found to be trespassing on their farms. Clearly, none of the limpets in the photo above are demonstrating any type of territorial behavior! So they are either some other species of Lottia, or are younger individuals of L. gigantea that haven't yet made the change from male to female.
In any case, I do think the pattern is very interesting, even though I don't understand it. Or maybe because I don't understand it. I'm always intrigued by something that I can't explain, which is a good thing because it means I don't get bored very often. If anyone reading this has an explanation for this pattern, let me know about it!
It has been a while since I've spent any time in the intertidal. There isn't really any reason for this, other than a reluctance to venture out in the afternoon wind and have to fight encroaching darkness. There's also the fact that I much prefer the morning low tides, which we'll have in the spring. However, this past weekend we had some spectacular afternoon lows, and although I was working on Friday and couldn't spare the time to venture out, I went out on Saturday and Sunday.
Saturday was a special day, because I had guests with me. A woman named Marla, who reads this blog, contacted me back in the fall. She said she wanted to do something special for her husband's birthday, and asked if I'd be willing to take them to the intertidal. It turns out that Andrew's birthday was around this past weekend, and he had family coming out from Chicago to celebrate. They picked the perfect weekend, because the low tides we had were some of the lowest of the year. So on Saturday I met up with Marla, Andrew (her husband), and Betsy (Andrew's sister) and we all traipsed out to Natural Bridges.
Taking civilians into the intertidal can be tricky, because they often come with expectations that don't get met. Like expecting to see an octopus, for example. I explain that the octopuses are there, but are better at hiding from us than we are at finding them, but that never feels very satisfactory. This trio, however, were fun to show around. The tide was beautifully low and we had fantastic luck with the weather. It had rained in the morning, but the afternoon was clear and sunny. I congratulated Marla on remembering to pay the weather bill. And the passing stormlet didn't come with a big swell, so the ocean was pretty flat. We were able to spend some quality time in the mid-tidal zone, with occasional forays into the low intertidal.
The typical Natural Bridges fauna--owl limpets, mussels, chitons, anemones, etc.--were all present and accounted for. Of course, there isn't much algal stuff going on in mid-January.
Ochre star, Pisaster ochraceus
Neogastroclonium subarticulatum, a red alga
Giant green anemone, Anthopleura xanthogrammica
Sunburst anemone, Anthopleura sola
Chiton, Nuttallina californica
Feather hydroid, Aglaophenia sp.
Limpets (Lottia scabra) and periwinkle snails (Littorina sp.)
Scytosiphon lomentaria, a brown alga
Owl limpet, Lottia gigantea
A coralline alga, Corallina sp.
Given the time of year (mid-January) and the time of day (late afternoon), the sun was coming in at a low angle. This was tricky for photographing, both in and out of water. However, sometimes good things happen, as in this photo below:
That's a big kelp crab (Pugettia producta) nestled among four sunburst anemones (Anthopleura sola). Kelp crabs are pretty placid creatures, for crabs, and usually take cover when approached. But this one remained in plain sight, holding so still that I thought it was dead. Even when I hovered directly over it and blocked the sun, it didn't move at all. Then it occurred to me that maybe he was having the sexy times with a lady friend. So I very carefully reached down and gave him a tap on the carapace. He flinched a little, so I knew he wasn't dead, but made no move to get away. And I caught a glimpse of a more golden leg underneath him.
Crabs live their entire lives encased in a rigid exoskeleton, and can mate only during a short window of opportunity after a female molts. Early in the breeding season, a female crab uses pheromones to attract nearby males. When a suitable male approaches, she may let him grab her in a sort of crabby hug. That's what this male kelp crab is doing to his mate. They may remain in this embrace for several days, waiting until the female molts and her new exoskeleton is soft. At that point the male will use specialized appendages to insert packets of sperm into the female's gonopores. The two will then go their separate ways.
We didn't disturb these crabs, and let them go on doing their thing. By now the sun was going down, so we headed back up and were rewarded with a glorious sunset.
It's no secret that I love pelicans. I love watching them soar low over the waves, where they are truly in their element. I love watching them plunge from the air into the water and then bob right back to the surface, because unlike their cormorant relatives, pelicans can't fly underwater. And I love watching them plunk around on land, where they are dumpy and awkward but still somehow elegant.
The other day I ventured out between storms to photograph birds. As per usual I ended up down at Natural Bridges, where pelicans were hanging out on the last remaining rock arch. They were well within the reach of my long lens, so I took a lot of photos.
The youngster managed a safe landing without knocking one of its compadres into the water. That isn't always the case--those wings can do a lot of damage. But the three adult birds on the left hardly seemed to notice, which means the youngster has learned how to stick the landing without disturbing everyone else in the vicinity. I'm sure that's a lot easier said than done!
The intertidal sculpins are delightful little fish with lots of personality. They're really fun to watch, if you have the patience to sit still for a while and let them do their thing. A sculpin's best defense is to not be seen, so their first instinct is to freeze where they are. Then, if a perceived threat proves to be truly frightening, they'll scoot off into hiding. They can also change the color of their skin, either to enhance camouflage or communicate with each other.
Around here we have a handful of sculpin species flitting around in our tidepools. Sculpins can be tricky to identify even if you have the fish in hand--many of the meristics (things you count, such as hard spines and soft rays in the dorsal fin, or the number of scales in the lateral line) used to distinguish species actually overlap quite a lot between species. The fishes' ability to change color means that skin coloration isn't a very reliable trait. When I was in grad school there was another student in my department who was studying the intertidal sculpins, and she told me that most of the ones we see commonly are either woolly sculpins (Clinocottus analis) or fluffy sculpins (Oligocottus snyderi). I've developed a sort of gut feeling for the gestalt of these species, but I'm not always 100% certain of my identifications.
Anyway, back to the camouflaged sculpins. The ability to change the color of the skin means that sculpins can match their backgrounds, which comes in very handy when there isn't anything to hide behind. Since the environment is rarely uniformly colored, sculpins tend to have mottled skin. Some can be banded, looking like Oreo cookies. The fish in this photo lives in a pool with a granite bottom. The rock contains large quartz crystals and is colonized by tufty bits of mostly red algae. There is enough wave surge for these fist-sized rocks to get tumbled about, which prevents larger macroalgae from colonizing them.
Other shallow pools higher up in the intertidal at Asilomar have a different type of rocky bottom. The rocks lining the bottom of these pools are whitish pebbles that are small enough to be tossed up higher onto the beach. I don't know whether or not these pebbles have the same mineral content as the larger rocks lower in the intertidal, but they do have quartz crystals. The pebbles are white. So, as you may have guessed, are the sculpins!
Other intertidal locations have different color schemes. On the reef to the south of Davenport Landing Beach, you will see a lot of coralline algae. Some pools are overwhelmingly pink because of these algae. Bossiella sp. is a common coralline alga at this location.
What color do you think the sculpins are in these pools?
Give yourself a congratulatory pat on the back if you said "pink"!
Sculpins aren't the only animals to blend in with coralline algae. Some crustaceans are remarkably adept at hiding in plain sight by merging into the background. Unlike the various decorator crabs, which tuck bits and pieces of the environment onto their exoskeletons, isopods hide by matching color.
Turning over algae and finding hidden creatures like these is always fun. For example, I saw these isopods at Pescadero this past summer. See how beautifully camouflaged they are?
Sometimes, when you're not looking for anything in particular, you end up finding something really cool. Last weekend I met up with students in the Cabrillo College Natural History Club for a tidepool excursion up at Pigeon Point. We were south of the point at Whaler's Cove, where a staircase makes for comparatively easy access to the intertidal.
It's fun taking students to the intertidal because I enjoy helping them develop search images for things they've never seen before. There really is so much to see, and most of it goes unnoticed by the casual visitor. Often we are reminded to "reach for the stars," when it is equally important to examine what's going on at the level of your feet. That's the only way you can see things like this chiton:
Mopalia muscosa is one of my favorite chitons. It is pretty common up and down the California coast. However, like most chitons it is not very conspicuous--it tends to be encrusted with algae! This individual is exuberantly covered with coralline and other red algae and has itself become a (slowly) walking bit of intertidal habitat. It is not unusual to see small snails, crustaceans, and worms living among the foliage carried around by a chiton. Other species can carry around some algae, but M. muscosa seems to be the most highly decorated chiton around here. I showed this one to some of the students, who then proceeded to find several others. A search image is a great thing to carry around!
Compared to the rocky intertidal, a sandy habitat can be a difficult place to live. Sand is inherently unstable, getting sloshed to and fro with the tides. Because of this instability there is nothing for holdfasts to grab, so there are many fewer algae for animals to eat and hide in. Most of the life at a sandy beach occurs below the surface of the sand, and is thus invisible to anyone who doesn't want to dig. There's a beach at Whaler's Cove where I've found burrowing olive snails (Olivella biplicata) plowing along just below the surface. I wanted to show them to the students, so I waded in and rooted around. I did find Olivella, but I also found a burrowing shrimp. I think it's a species of Crangon.
Now that is some damn fine camouflage! If the shrimp didn't cast its own shadow, it would be invisible. Even so, it was clearly uneasy sitting on the surface like that. I had only a few seconds to shove the camera in the water and snap a quick photo before the shrimp wriggled its way beneath the sand again.
As I've said before, observation takes practice and patience. To look at something doesn't mean you truly see it. That's why it is so important to slow down and let your attention progress at the pace of the phenomenon you're observing. If the only things that catch your eye are the ones that flit about, then I can guarantee you will never find a chiton in the intertidal. And wouldn't that be a sad thing?
Autumn is migration season in California. We all know that, in the northern hemisphere, birds fly south for the winter and return north for the summer. And indeed, this is a very good time to go bird watching along the Pacific Flyway, as migrating birds stop to rest and feed at places such as Elkhorn Slough. Here in Santa Cruz, autumn is punctuated by the return of monarch butterflies (Danaus plexippus), roosting in eucalyptus trees at Natural Bridges State Beach and Lighthouse Field.
Since 1997 the Xerces Society for Invertebrate Conservation has been tracking monarch sightings on their migrations between the western U.S. and Mexico. They conduct a volunteer butterfly count every Thanksgiving. More recently, community science data sources such as iNaturalist provide much of the information.
Xerces Society Western Monarch Thanksgiving Count. 2019. Western Monarch Thanksgiving Count Data, 1997-2018. Available at www.westernmonarchcount.org.
This morning, before it got warm, I went to Natural Bridges to see how the monarchs were doing. I wanted to photograph clumps of butterflies dripping from tree branches. It seemed, however, that there aren't as many butterflies as I remember from previous years. The clusters were not nearly as large or as dense as they should be. And the data shown in the figure below do demonstrate a precipitous decline in monarch since 2017. We're still a couple of weeks away from this year's Thanksgiving count, and there is still a chance that the butterflies might arrive in larger numbers.
Xerces Society Western Monarch Thanksgiving Count. 2019. Western Monarch Thanksgiving Count Data, 1997-2018. Available at www.westernmonarchcount.org.
Trained observers know how to estimate the number of butterflies in a cluster like this. The numbers of butterflies at various roosting sites are aggregated to assess overall population sizes.
This morning I did see one butterfly that had a tagged wing. It was wearing a green Avery round sticker, with some writing in what looks like black Sharpie. The color of the sticker was very close to the green of the surrounding foliage, so I wasn't even able to see the sticker until I downloaded the pictures from the camera.
At first I thought the tag resulted from an official scientific project or undertaking, but it turns out that anyone can tag a monarch. The tags are used to track migration of the butterflies. There doesn't seem to be a central depository of tags and their origins, so knowing the color of the tag doesn't tell me where this particular butterfly came from.
Once the sun hits the butterflies and they begin to warm up, the clusters start breaking apart. Butterflies open and close their wings, exposing the darker dorsal surfaces to the sun and warming up their flight muscles. Sometimes they dislodge one another.
On a cool morning like this, many of the butterflies that fell out of the clump couldn't fly yet, and landed on the ground. The boardwalk is perhaps not the safest place for a butterfly to wind up, but at least in a monarch sanctuary such as Natural Bridges the visitors are knowledgeable and look out for the butterflies' safety.
As I wrote before, the butterflies we see at Natural Bridges this year were not born here. This means that their survival to this point has depended on healthy conditions in the Pacific Northwest and the western slopes of the Rocky Mountains, where they lived as caterpillars and emerged from their chrysalises. This also means that planting milkweed for monarch caterpillars in California won't help the butterflies that we see here, although it would help butterflies that are destined to overwinter elsewhere. What will help local butterflies--monarchs and otherwise, and all nectar-feeding insects, in fact--is planting California native plants, to provide them with the nutrition they have evolved to survive on.
Sometimes dead things can be very informative. Not in the same way as their living counterparts, of course, but there are times when observing a dead specimen reveals details that cannot easily be discerned when the creature is alive. For example, most living birds don't let you get a close look at their feet. Dead birds, on the other hand, don't complain and try to maim you when you spread their toes and look for webbing. What does webbing have to do with anything? It tells you whether and how a bird swims, of course.
Cormorants are fish-eating predators. Like their relatives, pelicans, they do plunge-dive from the air into the water. However, cormorants are much more streamlined than pelicans and also chase their prey underwater. A bird locomoting in water has two options for propulsion--it can use its wings to "fly" underwater or use its feet to paddle along.
Take a look at the foot on that dead cormorant. It is clearly webbed, eminently suitable for a bird that uses its feet to swim underwater. The location of the feet also has functional significance. Note how far back they are on the bird's body. Obviously this helps increase the overall streamlining of the body. Now think about how submarines move through water: the prop of a submarine is also positioned on the back of the boat. That's probably not a coincidence.
Any trip to the beach brings opportunities to see creatures that have washed up. Or are in the process of washing up. Sometimes even (relatively) large animals end up beached. The big scyphozoan medusae, for example, have little control over where the currents take them, and find themselves in shallow water close to shore.
Animals made of jelly do not fare well when they encounter land. There were several of these dinner-plate-sized jellies drifting and pulsing lazily in very shallow water. A few had been left stranded by the receding tide and were already drying up. Even the ones that were still alive would probably never get back to deeper water. Fortunately for them, they are blissfully unaware of their imminent demise--sometimes lacking a centralized nervous system with its all-knowing brain would be a blessing.
Death, of course, is a part of life and a very important part of nature. Even knowing that, it can be disturbing to see dead animals washed up on the beach. For most people, the shells and whatnot of invertebrates don't seem to count as dead things, but everybody recognizes a dead bird. And there is a natural human tendency to feel sorrier for things that are more like us. From a biologist's perspective, keeping track of dead animals on beaches can give us a lot of information about conditions in the sea. There is a sort of standard death rate, but deviations above what is considered normal may signify that something is going on. There are volunteers who make monthly patrols along beaches in the Monterey Bay Area, collecting data on the various carcasses that wash up. These data are used to evaluate the overall health of the waters within the Monterey Bay National Marine Sanctuary. Knowing about dead things can teach us about what's going on with the living things.
