Sunday, May 28, 2017

A Visit to the Southwest Wildlife Conservation Center

It is becoming increasingly important that we communicate to the public the reasons that we have wildlife in captivity. A vital part of that story is giving a home to animals that have been injured or mistreated and cannot be returned to the wild. We were privileged this past week to visit one of the Desert Museum's sources for just such animals - The Southwest Wildlife Conservation Center in far northeastern Scottsdale.

In business for over 20 years, the center began with one injured coyote taken in by Linda Searles, the founder and Executive Director, and has grown into the 10-acre operation of today with over 100 rescued animals. If the animals can be rehabilitated and returned to the wild, they are kept in a separate area from those who cannot. The center is very careful to not allow those animals to become habituated to or imprinted on humans, so contact with them is strictly limited. The animals that we observed were those which can never return to the wild and are given sanctuary at the center. The reasons for that range from permanent injuries, mistreatment, being kept illegally, habituation to humans, given a death sentence (3-strike bears, wolves condemned for preying on livestock), etc. The center works closely with Arizona Game and Fish Department on rescues and confiscations. They have a small paid staff, a large contingent of volunteers and several contract veterinarians. A recent addition is the new veterinary center.

The center's mission is . . .

Southwest Wildlife rescues and rehabilitates wildlife that has been injured, displaced, and orphaned. Once rehabilitated, they are returned to the wild. Wildlife education includes advice on living with wildlife and the importance of native wildlife to healthy ecosystems. Educational and humane scientific research opportunities are offered in the field of conservation medicine.  Sanctuary is provided to animals that cannot be released back to the wild.

The animals we visited included Mexican gray wolves, foxes, coyotes, a large sulcata tortoise, mountain lions, bobcats, javelina, white-tailed deer, black bears, coatis, and one leopard-jaguar hybrid. Each one had an interesting, mostly heartbreaking story to tell, as related to us by our volunteer tour leader, Tara. Black bears whose mothers had been shot as a result of being habituated to humans; Leo, the leopard/jaguar hybrid who was bred for the entertainment industry and then sold to a roadside "zoo" in Douglas, Arizona; a mountain lion who was kept illegally as a pet (seriously?!). Our black bear, Strawberry, came from SWCC as did one of our coyotes and one of the beavers. Sometimes the animals go the other way, as in the case of three kit foxes, the Pepper Brothers - Chili, Hatch and Jalapeño, who were sent to SWCC by the Desert Museum.


The center depends wholly on donations and tour revenue for its financial support. That revenue stream was severely curtailed in the last couple of years as a result of a new neighbor. As far out in the desert as this location seems, houses are quite close to them. They prided themselves on their good relations with their neighbors. But that was shattered when a new neighbor moved in and promptly filed a zoning complaint against the center, saying that they did not have the proper zoning to be conducting tours for the public. And he was right. They had to immediately cease giving tours. That financial blow was compounded by further legal action by this neighbor over noise (coyotes and wolf howls!) and dust complaints. Late last fall, Maricopa County Board of Supervisors granted SWCC a Special Use Permit, allowing for the resumption of tours and school group visits. This was good news, but the conflict with the neighbor continues.

See the video of the black bears having a snack.

I believe that all of the docents who visited the center were quite impressed with the facilities and with the dedication of the staff and volunteers to the welfare and well-being of the animal population. The center's website contains extensive information about the animals, the history, the legal battles, education programs and the philosophy of SWCC. ASDM is fortunate to have this resource, and so are the animals who depend on it for their existence. Check out this link to the Southwest Wildlife Conservation Center and read about all their programs.

Wednesday, May 24, 2017

Mobbing Behavior in Birds

One Friday at the Desert Museum, another docent and I separately witnessed an interesting interaction between a raven and a smaller raptor, most likely an accipiter (Cooper’s hawk or sharp-shinned hawk).  The larger bird was harassing the smaller one.  It’s more common to see small birds attacking or harassing a larger raptor.  This behavior is known as mobbing, and, although it’s most frequently seen in birds, other animal species use similar tactics.

Mobbing is an antipredator technique used by a prey species against a predator, most commonly to protect their offspring.  The goal of the prey species is to drive the predator from a nest, breeding territory or non-breeding home range, or even a food source.  Mobbing takes place most often in the spring, coinciding with breeding and nesting. Sometimes mobbing is employed to distract and steal food from another bird. Another important function of mobbing is to teach younger birds to distinguish friends from foes. A recent study indicates that mobbing may also give male birds the chance to show off their physical qualities to impress females. 

The most common targets of mobbing include hawks, eagles, crows, ravens, herons, and owls.  Those doing the mobbing (mobsters?) include chickadees, titmice, kingbirds, blackbirds, grackles, jays, crows, ravens and even other raptors.  Mobbing behavior can include chasing, dive-bombing,
bumping, loud squawking, defecating or vomiting on the predator, and may be done by a single bird or a group.  The loud calls often attract more birds of the same species to join in on the harassment. 

Several years ago, I felt very lucky when a great-horned owl chose one of my large trees in which to roost.   It wasn’t long, however, before I began to hear the incessant alarm calling of a Cooper’s hawk.  I discovered the Cooper’s hawk perching nearby and constantly tormenting the owl.  Eventually, the owl moved on to somewhere more peaceful. The Cooper’s hawk, who had a nest not far away, had achieved her goal, removing the predator from the area.  In fact, one way to find perching owls is to listen for the loud calls of mobbing birds. 

By its nature, mobbing by small birds of a large, dangerous predator seems to be a courageous or foolhardy act.  Researchers don’t completely understand why predators don’t turn and snatch up one or two of the tormentors, which would presumably put an eventual end to the behavior. Since mobbing persists, it suggests that surprise is an essential element in raptor hunting. 

Next time you hear loud bird squawking, check the skies for some fascinating bird behavior.


All About Birds: Mobbing Behavior

Mobbing Behavior: Wikipedia

Stanford Birds - Mobbing 

Science Daily: Birds of a feather mob together

Wednesday, May 10, 2017


Last week, fellow docents and I were having a conversation, prompted by a question to one of them from a visitor, regarding the relationship between a palo verde and a saguaro. It was obvious from our discussion that we needed a review of symbiotic relationships!

Symbiosis is defined as a relationship between two or more organisms that live closely together. There are three main types of symbiosis: commensalism, mutualism and parasitism. Commensalism is a relationship in which one organism benefits and the other is unaffected. Mutualism is a relationship in which both organisms benefit. Parasitism is when one organism benefits and the other one is harmed. To be successful, a symbiotic relationship requires a great deal of balance. Even parasitism, where one partner is harmed, is balanced so that the host lives long enough to allow the parasite to spread and reproduce.

These delicate relationships are the product of long years of co-evolution. Bacteria were the first living things on the planet, and all of Earth's other creatures have been living and evolving with them for hundreds of millions of years. Today, microbes are essential for many organisms' basic functions, including nourishment, reproduction, and protection.

So, back to the saguaro/palo verde relationship. The visitor wanted to know, if the nurse tree was benefitting the saguaro, what the payoff was for the palo verde? How would you classify that? The saguaro benefits from the protection provided by the palo verde. But, how about the palo verde? Most of the time, their relationship is probably commensal - benefiting the saguaro and causing no harm to the palo verde. However, in times of drought the shallower root system of the saguaro may intercept most of the rainfall.  These two species would then be said to enter a type of symbiosis known as interspecific competition. The saguaro could eventually hasten its nurse tree's death.  

There are thousands (millions?) of symbiotic relationships in the Sonoran Desert. Just take the saguaro, for example. Think of all the animals that depend on the saguaro for food, or shelter. The saguaro, in turn, depends on certain species to pollinate it, and to disperse its seeds. Bees, bats and white-winged doves get a food reward, while doing the important work of helping the saguaro to reproduce.

Parasitism - The desert mistletoe is an example of a parasitic symbiont that depends on its host,

usually a legume tree, for nutrients. The host tree is harmed over time and with heavy infestation of the mistletoe by the depletion of nutrients. 

Other common parasitic relationships include the coyote and the flea, or the mange-causing mite. Female mites can burrow into the skin. Coyotes with mange can lose their hair, which can make it difficult for them to control their body temperatures. Mange must be extremely severe before it disables a coyote. Most coyotes can survive with the disease for a long time. The brown-headed cowbird parasitizes the nests of other birds, called brood parasitism. The cowbird benefits by having another bird raise its young, which are usually larger than the bird’s own young and can out-compete them for food and space.

Animals are parasitized by viruses, bacteria, fungi, protozoans, flatworms (tapeworms and flukes), nematodes, insects (fleas, lice), and arachnids (mites). Plants are parasitized by viruses, bacteria, fungi, nematodes, and a few other plants.

Mutualism - Examples of mutualism abound. Just think about flowers and their pollinators. That’s a
win-win for both parties. Not all symbiotic relationships are visible by humans. Take the bacteria that live in the guts of herbivores, helping them to digest plant material, which is more difficult to digest than animal prey. This gut flora is made up of cellulose-digesting protozoans or bacteria living in the herbivores' intestines. Another example is the bacteria that allow legumes to fix nitrogen in the soil, living on nematodes on the plant roots.

Commensalism - Commensal relationships may involve one organism using another for transportation or for housing or it may also involve one organism using something another created, left after its death (metabiosis). Examples of metabiosis are hermit crabs using gastropod shells to protect their bodies. Birds nesting in trees is a commensal relationship. Vines use trees to reach up to the light, causing no harm to the tree (most of the time!).  Consider the packrat home and all the many critters that seek shelter and food there.

Symbiosis can either be obligate or facultative (optional). In obligate relationships, one organism cannot live without the other. Perhaps one of the most well-known obligate mutualistic relationships is that of the yucca moth and its host plant.

The yucca moth, also commonly called the pronuba moth, is a small white moth that lives in the semi-arid habitats where yucca plants grow. The yucca moth is well-known for its co-dependent relationship with the yucca plant. The yucca moth’s larvae rely exclusively on the seeds of the yucca plant as a primary food source, and the plant relies exclusively on the yucca moth for pollination. One cannot exist without the other, creating an obligate mutualism between the moth and the plant. 

We talk about Keystone Species - a plant or animal that plays a unique and crucial role in the way an ecosystem functions. Without keystone species, the ecosystem would be dramatically different or cease to exist altogether. These are species on which so many other species are dependent. Think about the saguaro, and prairie dog, and the many different species for which they are so important. Another good example is the cottonwood tree and the many creatures that depend on it. I’m sure you can think of many more relationships in biology, for I haven’t begun to scratch the surface.  I have discussed only the 3 main types of symbiosis.  There are many more, and perhaps those are topics for another article.

We do well to remember that in each of these types of symbiosis, few situations are absolute.  In most cases, there is a continuum of types of interactions between species, rather than an exclusive category.