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West Nile virus

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Condor Chick Fostering: 30 to 45 Days

The growing chick has lots of feathers to play with.

The growing chick has lots of feathers to play with.

At a little over 1 month of age, our California condor chick should weigh around 4.5 pounds (2 kilograms) (see previous post, Condor Chick Fostering: 1 Week to 1 Month). The foster parents, Towich and Sulu, have started leaving the chick alone overnight, sleeping near the nest. If the weather is still cool or it’s raining, the parents may brood overnight until the weather improves. Even though the parents are increasing their time away from the chick, they remain VERY vigilant and protective of their nest and, especially, their chick. Some field biologists have even seen wild condor parents chasing black bears away from the nest area!

Up until now, the chick has been scooting around the nest on its tarsal joints—we call it the tarsal crawl. It’s not uncommon, at this age, to see the chick standing all the way up on its feet, teetering around the nest, holding its wings out for balance. As its legs get sturdier, the chick may even approach the parent, begging for food. The wing-begging behavior we’ve been seeing gets more pronounced: lots of wing-flapping, head-bobbing, and trying to position itself in front of the parent.

It is possible that the parents, who are offering larger quantities of food per feeding session, might be providing a small amount of fur/hair in the chick’s diet. (Part of the adults’ diet includes mammals, like rats and rabbits.) Condors can digest just about every part of the animals they eat, except for fur. This fur accumulates in the digestive tract and is eventually regurgitated as waste. We refer to this as casting. A condor’s cast is composed of predominantly fur, whereas a cast from an owl has fur and bones; owls can’t digest bones, but condors can. We have seen condor chicks cast hair pellets as young as three weeks of age. When the chick casts, it throws its head forward several times, mouth open, until the pellet is ejected from its mouth. It can look like the chick is in trouble, but it is perfectly normal, and good for the chick.

At 45 days of age, or around June 12, the chick will get its first health exam. We will obtain a blood sample for the lab to make sure it is healthy and to determine if the chick is male or female. Also, during the exam, we will weigh the chick—it should weigh between 7.7 and 8.8 pounds (3.5 and 4 kilograms)—and inject a transponder chip as a form of identification. It’s the same kind of chip you can get for your dog or cat. Most importantly, this exam allows us to administer a vaccine for West Nile virus, a disease that originated in Africa and was accidently introduced to North America by humans. North American wildlife, including condors, usually doesn’t have a natural immune response to West Nile virus, so we are trying to give the chicks as much of a head start as we can.

This exam will be the first time that the chick will see humans, so it will naturally be disturbing for it. We try to be quick (9 to 10 minutes) to minimize the disturbance. Additionally, we will keep the chick covered with a towel to reduce its exposure to humans and to provide it a bit of security. Towich and Sulu are usually away from the nest when we perform the procedure, to keep them as calm as possible as well. We don’t want the chick to become accustomed to or feel reassured by our presence; we want it to be a wild condor, uninterested and wary of humans, so that it may someday fly free in California, Arizona, or Mexico.

The chick will look very large at this age compared to how big it was at hatch, but remember that it is still less than half of its adult weight. There is much more growth and fun to come on Condor Cam!

Ron Webb is a senior keeper at the San Diego Zoo Safari Park.

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Counting Mosquitoes

Summer interns Kathleen Connolly, left, and Christina Mangan pose with some of their finds.

Since October 2011, we have been monitoring disease vectors in the Safari Park Biodiversity Preserve (aka The Back 900). Here, the valuable coastal sage scrub habitat has been undergoing cactus restoration as well as monitoring of one of its important inhabitants, the cactus wren (see post Cactus Wrens Rise from the Ashes). Our goals are to monitor the presence and activity of mosquitoes and midges, two important disease vectors, and test them for West Nile virus and blood parasites, including plasmodium, the cause of avian malaria, in and around this reserve. From this data, we will be able to look at the occurrence of these disease agents in insects within the cactus wren habitat and which mosquito or midge species act as likely vectors.

Another interesting aspect of this study is analyzing what hosts these insects have been feeding on by evaluating their blood meals. Only females feed on blood; the male mosquitoes and midges feed on nectar. So for this study we are only concerned with the female insects. DNA is extracted from the blood meal, and a barcoding PCR is performed. The PCR product sequences are then compared to published sequences in the Barcode of Life database, which contains DNA sequence information for a large number of animals. Finding a match between the DNA sequence extracted from the blood meal and a known DNA sequence will enable us to determine which animals these insects have been feeding on. Mosquitoes and midges within the Safari Park have been found to feed upon various local creatures, including mallards, desert cottontail rabbits, mule deer, humans, and an occasional collection animal.

So, how do we convince the insects to be tested? Once every other week, our summer interns and I go out into the field, setting up UV traps and CO2 traps to attract and capture mosquitoes and midges. While out in the field, it can be quite an adventure, from the bumpy roads and rolling hills to the occasional visit from a resident mule deer or a speeding roadrunner. It is often enjoyable to get out of the laboratory and into the field and observe virtually undisturbed habitat right in our own Park’s backyard.

The UV traps attract the mosquitoes by emitting a UV light of about 350 to 400 nanometers; this acts as a visual stimuli for the mosquitoes and midges. The CO2 trap contains dry ice that emits CO2 to mimic the respiration of an animal and works as a chemical attractant for the insects. After anesthetizing the insects back at our Wildlife Diseases Laboratory, the students then have the arduous task of tediously counting and identifying the various species of mosquitoes and midges. Later, they extract the DNA and RNA from these insects and utilize it for the PCR testings.

This project has given our interns the opportunity to gain experience in the laboratory and in the field!

Jennifer Burchell is a research coordinator for the San Diego Zoo Institute for Conservation Research. Read her previous post, Invisible Clues.