Sunday, June 26, 2011

It's a lizard, not a toad

In June when Saguaro fruit are ripe, ants come to feast on them and Horned Lizards emerge from hiding to feast on the ants. When I posted my first image of a juvenile Regal Horned Lizard (Phrynosoma solare) to the photo gallery of the Arizona Star and sloppily called it a Horned Toad, Doris Evans, a teacher and long time Arizona Sonora Desert Museum docent corrected me right-a-way. We have become a good friends since then.

So: it's a lizard, of course. Even if he's short and round and waddles a little bit like his neighbors, the Sonoran Desert Toads, the scaly skin and his complete independence of water mark him clearly as a reptile. See his regal dragon profile above! His English name 'regal' and the Latin 'solare' (sun-related) both refer to the full crown of spikes of our Sonoran Desert species. 

Photo from the AZ Star Gallery (Photographer's name will be added)
After mating in the middle of the hottest season the female of our low desert species lays up to 33 leathery-shelled eggs in an underground chamber that she has prepared in the sandy soil.

After hatching, the little ones are on their own. They are vulnerable to many predators, so the large clutch numbers are not excessive.

Photo by Collins L. Cochran who allowed me to use it
High in the Catalina Mountains, a close relative, the Greater Short-horned Lizard, gives life birth to even more babies - up to 48 per clutch. In a lizard, giving live birth means nothing more than laying very thin-shelled eggs that rupture during the birthing process to release the fully developed young (Ovoviviparity). This may be an adaptation to the difficulty to bury eggs among those rocks and low night time temps that might interfere with egg development.

Extremely spiky scales make it difficult for predators to swallow the lizard whole. Smaller youngsters do get gobbled up in numbers by voracious Roadrunners and hungry Kestrels.
In addition to being spiny, the fully grown lizard, when threatened, makes himself very flat and wide. I have been able to rescue several from our Husky, who is a terrible predator constantly prowling for extra food, because she just couldn't get a grip on the flattened disk. 

None of those horned lizards that the dog attacked and even one that she retrieved in her mouth used the defense against canines described in literature:  attacked horned lizard are said to spray 'blood' from their eyes - as far as a foot! I found this impressive video.

Illustration in the book 'Horny' by Emery and Le Blanc 1968
 This story always made me wonder. Spraying blood may deter a squeamish human. (Although according to a 1912 story republished in our newspaper to celebrate 100 years of AZ statehood, postal clerks at that time  had to routinely liberate numerous 'Horny Toads' that Tucsonans were trying to illegally ship to their friends out East. So those though human Westerners didn't get scared off....)
A well aimed squirt of any fluid as shown in the illustration above might scare off most inexperienced canines, but I still suspect that the spray isn't really just blood.

Photo by Bill Gorum
When I did my postdoc at the physiology department of the University of Arizona we speculated that the source of the excretion may be the extraorbital gland situated above the eyes of reptiles and birds. In seabirds like Albatrosses and reptiles like sea turtles, who have no access to fresh water, these salt glands, with a much higher concentration capacity than the rather simple avian and reptilian kidneys, are responsible for elimination of excess salt from the animals' blood stream. So the fluid constantly running down (on the out side of) a seabird's  nose is a brine much more concentrated than either sea water or blood. As a desert creature with limited access to water the horned toad also uses salt glands. So could it be that the horned lizard is ejecting something more concentrated than blood? But, salt gland excretion itself is neither red nor pressurized...So that's not the answer.

Photographer Dave Beaudette: Adult, squirted blood from its left eye when I removed it from the road, Las Cienegas National Conservation Area, Pima County, AZ, 18 June 2009
 Wade Sherbrooke (Sherbrooke 1981) describes a complex vascular mechanism that allows the lizard to increase the blood pressure in parts of their head. This pressure difference between head and body has other functions in thermoregulation and molting, but as part of this unique a defense mechanism it can also produce a fine stream of blood originating from the blood sinuses located in the eye sockets. The discharge seems directional and can reach a distance of up to four feet. This still doesn't explain why coyotes and other canines don't just lick their lips and pounce on the tasty morsel, but react with violent head shaking,  excessive salivation and signs of distress. Maybe the supraorbital salt glands, located so close to the blood sinuses where the spray originates do have something to do with it after all, or maybe the lizard's diet, consisting mainly of ants, some of witch carry potent poisons of their own, is the source of some distasteful chemical in its blood.
PS: Eldon Braun just sent me the paper of a study on the composition of the ejected blood: It is just about identical to the systemic blood in hematocrit, osmalilty, sodium and potassium content.  But coyotes reject food laced with the ejected blood, but not if systemic blood is mixed into the food.

By far the most successful and much less costly protection of the horned lizard is his amazing camouflage. His color and pattern brake up his shape and blend with the sandy ground. Even the spiny scales look just like sharp edged rocks, and the middle stripe that of this individual echoes the dead creosote twigs so successfully that I kept losing him in plain sight, specially when he moved around in his typical stop-and-go-and-freeze pattern of motion.

His eyes are shaded under heavy ridges and often half closed, so they don't draw attention to him either.  In his usual pose the body is pressed against the ground and a flaring fringe of spiky scales along the sides eliminates any cast shadow. If he has to straighten up, the light color of the underside acts as counter-shading that reduces his optical three-dimensionality from above (and most of his predators are taller than he).

In this last photo, he abandoned his cryptic behavior for a moment. At very high temperatures, all our lizards  minimize the contact with the hot ground by standing high on their legs and even lifting their toes off the ground. But the horned lizard also uses this pose as a threatening bluff when a predator (probably my camera in this case) molests him too much. (Note how the cast shadow now betrays the lizards location!)

Watercolor by the author of a Regal Horned Lizard feeding on Harvester Ants.
 Horned Lizards make a very difficult subject for a painting. An animal that developed attributes to make even its shadow inconspicuous and distort its shape does not stand out well on watercolor paper.

Literature: Horned Lizards, Unique Reptiles of Western North America by Wade C. Sherbrooke, publisher: Southwestern Parks and Monuments Association 1981

Comparison of Blood Squirted from the Circumorbital Sinus and Systemic Blood in a Horned Lizard, Phrynosoma cornutum. GA Middendorf, WC Sherbrooke, EJ Braun, The Southwestern Naturalist (2001) 46(3):384-387

Sunday, June 19, 2011

Arizona Wild Cats (and other wildlife) in Watercolor

The encounter with the bobcat at Sweetwater reminded me of my old habit of interpreting adventures like that in watercolor. Dissatisfied with just photographs, I began this kind of painting during my postdoc at the University of Trondheim in Norway. My flickr album 'Norwegisches Bilderbuch' shows those northern impressions.

Stylistically, the images were narrative and often composed from memory. They tended to focus on an animal encounter and place it in a setting that seemed most typical, but wasn't necessarily realistic.

I one of my first Tucson paintings, the American Kestrel has a background showing of the south side of  the Catalina Mountains but with the vegetation of the grasslands around Oracle.

After only a month in Arizona crammed the shapes of all the cacti that impressed me so much into a painting of a Coyote that had crossed my path close to Gates Pass.

 At that time, the introduction of Colorado River Water was a problematic topic in Tucson, so I painted my Acorn Woodpeckers in front of a little fountain at the Madera Canyon Lodge and titled it 'CAP Water?'

The Roadrunner was probably a great grand father of the two guys that I just photographed at Sabino Canyon. He was as unafraid of humans as thy are and chased his lizard up a mesquite tree right at the visitor center (which was much less imposing back then).

 On a hike to Weaver's Needle in the Superstitions I saw Collared Lizards running on their hind legs like miniature dinosaurs, but the one that held still for a reference photo was a female from the Arizona Desert Museum. I don't remember why I chose such a saturated green for the background - maybe just to show off her colors. Hard edged and overly detailed, she makes me cringe a little now.

I liked the ASDM settings with their carefully constructed artificial rock formations so much that I painted bobcat and bighorn sheep there before I ever saw them in the wild.

Later, at the creek at Madera Canyon, I walked right into a bobcat that looked much more impressive than the ones in captivity. By the time I painted him though, I had just been in some aspen forest around S. Francisco Peaks, so the slim silver trunks appeared in the background.

As developments encroach on their territory, bobcats are becoming quite used to people and their patio furniture. The portrait was half finished when its subject slid of an Orovalley friend's chaiselongue, so I had to finish it from photos.

I liked his face so much that I even included him in a series of paintings on river rocks. This heavy rock had a diameter of more than 12 inches.

I waited for years for an encounter with a mountain lion and delayed that tempting motive. At a ranch on the San Carlos Apache reservation I even rode along with hunters who were after a cattle-thieving lion, found huge tracks, lots of skunks, and a porcupine... I still haven't seen much more than the blur of a fawn shape leaping up a slope above the Lodge at Canyon d' Chelly - but I clearly saw a long tail trailing behind - so what else could it have been?

I then painted one from a photo and one with my easel set up at the Mountain Lion enclosure at the Phoenix Zoo. A critic later suggested a more contrasting background to make the cat stand out better. But that just didn't feel right.

 All the paintings above, with the exception of the bobcat portrait, are 10 to 20 years old, and so is the photo, taken in my first little apartment on Swan and River Rd. My painting style and choice of topics has changed since then, but I still enjoy the memories contained in the old images.

The original paintings were sold to private collectors. The copyright is owned by me, and cards and prints are still available.

Friday, June 17, 2011

Sweetwater Wetlands Morning in June

This morning I had Sweetwater Wetlands all to myself.  It's probably  hot enough now to keep most birdwatchers away. 

At first there wasn't much going on. Lizards rustled in dry  leaves,  mostly Whiptails darting around but also Zebra Tails and Desert Spiny males that are getting very territorial at this time of the year. 

Blue Dashers were involved in a never ending game of musical chairs around their perches. What makes one Cat-tail blade so much more desirable than another?

Young Round-tailed Ground Squirrels were playing close to their burrow's entrance and digging out shallow holes to cool their bellies. A Towee was scratching under a huge willow. 

 Suddenly a shrill whistle from the squirrels and right in front of me a larger shape appeared in the dappled light.

I hadn't seen him coming, but he was only about ten meters from me in the middle of the path: a bobcat. He checked me out for a moment, decided that I was harmless, and kept coming. When he passed me, he was not even six feet away. A little scrawny looking, and panting from the heat....The squirrels were sitting at a save distance, watching like statues.

Please, check out all of the Sweetwater critters in this video. The bobcat makes his appearance towards the end! 

A Cooper's Hawk was patiently waiting for me to leave. Definitely a day with lots of predator sightings. I hope the little squirrels stayed alert and careful.


Wednesday, June 15, 2011

Another Backyard Snake: The Western Patch-nose

The temperature was supposed to climb to 105 degrees today, so I was hand-watering some smaller cacti. They may not need it, but they get less sunburned when they are well hydrated and at least it makes me feel better. I nearly missed the sleek, striped body of a snake among a group of little golden barrels because it looked just like a dry branch of creosote. Then my first thought was Whipsnake, so I had little hope of getting close to that extremely wary, lightning quick reptile. I checked later: the Striped Whipsnake occurs further north, and the Sonoran does not have a striped body.

This snake allowed me to crawl around the creosote bush and photograph its blunt face with one big scale covering the snout - clearly a Patch-nosed Snake. Our land in the bajada of the Tucson Mountains is the typical desert scrub habitat of the species called Western Patch Nose Salvodora hexalepis, while the Eastern S. grahaminae prefers the open slopes of the Evergreen Woodlands. The mottled double stripe visible in the top photo confirms the identification.

The big scale that protrudes slightly over the sides of the snout is probably useful when the snake digs in the ground for reptile eggs. The day active snake also feeds on lizards and small mammals. I was happy to see him, but I hope he will not be too hard on our drought stressed lizard population.

Tuesday, June 14, 2011

'Raubritter' among Insects

Stenopogon inquinatus male
The German word 'Raubritter' has no good English translation that I know of. In lawless medieval times rogue knights were sitting in their fortified castles along European trading routes, ready to capture, rob and often slay passing travelers. Similarly, robber flies perch by day on objects near the ground, watching every movement in clearly binocular vision, always ready to fly up and strike at any insect prey that passes by in the air.

Stenopogon inquinatus female
Last week on our trip to Mount Lemmon, the highest peak of the Catalina Mountains, Eric Eaton and I  found some exceptionally large specimens. The one in the picture above had just caught a grass hopper of the species Trimerotropis modesta.  The fly had grabbed it, injected its paralyzing digestive juices through its pointed proboscis and then sucked out the dissolved tissue of the grasshopper. After the robber fly had finished its meal, the exoskeleton of the grass hopper seemed mainly intact.

Trimerotropis modesta
The robber fly below has caught a honey bee by grabbing it by the thorax and holding it in the firm grasp of its bristly legs so the bee had no chance to sting. The bristles at the tip of the female's abdomen, called acanthophorites, help her to push the abdomen into the soil to lay her eggs.

Stenopogon inquinatus female
There are nearly 1000 species of robber flies (Asilidae) in North America, and most of them live in the hot, arid Southwest.The family has members of all sizes from 3 mm up to 5 cm.

It seems understandable that we found several very large species on Mount Lemmon: Like many  insects robber flies stake out  territories on local high points (hill tops) of the terrain, and size and strength are great advantages in the constantly whipping wind on Mount Lemmon that could easily rip any hunter or courting male off its exposed perch.

Laphria engelhardti
Around Tucson, bumble bees occur only in the higher elevations. They share the mountain habitat along the Meadow Trail with  Laphria engelhardti, one of the many bumble bee mimics in the genus Laphria. When startled, it flies only for a few feet, very low over the ground, so the strong wind can't catch it.

Eccritosia zamon
I photographed this pair at the end of August 2009 on a hill top along the north side of Sabino Canyon.

As with many powerful predators, the male has to take quite a risk when he approaches the female to mate. Usually they seem to approach from above and behind and grab the female before she can go on the attack. Asilid males haven't come up with the gift-bearing trick that some other relatives in the fly family use, but it doesn't hurt to find the female already busy with prey. In this case the mating couple devoured the yellow jacket together.

Wyelia midas

The sting of an asilid fly is supposedly very painful, but obviously it doesn't hurt to advertise this by wearing the colors of another famously pain-inducing stinger, the Tarantula-Hawk Wasp (Muellerian mimicry). At the same time, this robber fly evokes in color and sluggish flight very much a harmless Midas Fly which also finds protection from predators in its similarity to the wasp's appearance (Batesian mimicry). So the robber fly, like a wolf in sheep closing, maybe fooling its prey as well as its predators.
Archilestris magnificus

The largest of our robber flies  I have not found in the high  Catalinas, but in lower areas further south along the Santa Cruz River in Amado, in the grassland of lower Madera Canyon and along Highway 90 towards Sierra Vista. There, several times I had the chance to watch two of these guys pursuing each other for whatever reasons - an impressive aerial dance. Dr Scarborough pointed out that the identification of this species may not be quiet certain - so I'll call it Archilestris near magnificus.

Thank you to Prof. emerit. A. Scarborough for his help with the identifications.

Friday, June 10, 2011

Firefly without a flash: Pyropyga nigricans

When I walk to the entomology department in the Forbes building on the U of A campus, I pass well irrigated manicured lawns. Since the end of May, little black insects were flying there. They first reminded me of March Flies until I saw the spread elytra - they were clearly beetles. It's an interesting experience to chase down a flying object with a somewhat erratic course, too small to be noticed by most humans, while walking among students absorbed in texting and phone conversations. It makes them emerge from oblivion and stare...Finally I swiped my hat in flamboyant musketeer fashion and caught one.

The narrow dark beetle is about 8 mm long, soft bodied, has flattened antennae and the head is hidden under the half-circular thoracic shield with a continuous  black border, rosy sides and a wide black middle stripe. This is Porpyga nigricans, a very common western firefly or lampyrid beetle.(The western distribution of P. decipiens, 4.5-7.2 mm is unclear. P. minuta is smaller and its US distribution ends further east). 

Adult fireflies in the genus Pyropyga are day active and have no luminescence. Both sexes are winged (aleate) and can fly, but specimens with reduced wings have been found, too. Males and females find each other with the help of pheromones. In captivity the larvae have been raised on snails and small earth worms. I guess the irrigated lawns offer a similar diet. I've never seen any Pyropyga around our house in the desert but I have photos of a specimen from the research station in Portal where there are ponds and swamps (when the water isn't used up to fight forest fires).

The heamolymph of Fire Flies contains lucibufagins (Eisner et al. 1978), steroidal pyrones. Droplets can be expelled from joints and membranous parts of the exoskeleton as a defense against predators and birds and lizards show strong avoidance of these beetles. As many other poisonous insects, Propyga also has its mimics:some Soldier Beetles (Cantharidae) and  Netwing Beetles (Lycidae) look very similar to Porpyga and may also be poisonous in their own right (Muellerian Mimicry enhances the effectiveness of the warning color/pattern for all of them).

P.s. mating activity is high in August on the lawn of a fraternity house on University Boulevard, that always irrigates the lushest lawns in the neighborhood.

Eisner et al., 1978. Lucibufagins: Defensive steroids from the fireflies Photinus ignitus and P. marginellus (Coleoptera: Lampyridae). Proc. Natl. Acad. Sci. USA 75: 905-908.