snail

Why did these coyotes attack?

California Death Valley Coyote)The Question: Why did coyotes attack me and my dogs?

Submitted by: Jessie, Arizona, USA

(click on photos and graphics to expand)

The Longer Question from Jessie: “I live in central Arizona, and was out walking my three dogs on a rarely used trail at approximately 8:30 a.m. Part of the trail passed by a pool of water, which is rare in the area I was hiking in. As I was passing, a coyote appeared about 30 feet away and started vocalizing and making itself as visual as possible. I stopped for a few seconds, expecting it to run away as has happened with every other encounter I’ve had with a coyote.

“Instead, approximately eight other coyotes silently circled in and tried to attack us. They were lunging within four to five feet of my dogs and I. My dogs were terrified and just froze, so there was no aggression on their part. I started yelling and throwing rocks at the coyotes, but they had no fear. I am on the short side and only weigh 70 lbs, so that may have been a contributing factor.

“We somehow broke out of the circle, but they continued to follow us for about ten minutes. Two or three would emerge from the junipers, backs hunched and vocalizing while the rest of the pack positioned themselves to emerge somewhere ahead of us on the trail. They were quite brilliant in their strategies.

Coyote_arizona“Is this typical coyote pack behavior? Is it strange to have such a large pack? Were they trying to hunt us or were they just protecting a rare source of water in the middle of the desert? I’ve only ever seen coyotes as lone individuals, or in pairs, and they’ve always been timid.”

The Answer: Jessie’s description of facing these coyotes (Canis latrans) sounds terrifying, and I’m glad she kept her head under these condition. I asked Paul R. Krausman, a Certified Wildlife Biologist at the University of Montana, who studies coyote behavior and human and coyote interactions, for his thoughts on this situation. Here’s what he said:

“What Jessie describes is an interesting situation, and one that could have been troublesome. It is unlikely they were protecting the water. Predators will use water when available, but are adept at obtaining moisture from their prey.

“The large pack could have been a female and her pups with one or two others and their intent was likely to attack the prey (the dogs). The owner’s attempt to discourage the coyotes by tossing rocks may have been more of a deterrent than she knew. Coyotes do hunt in packs and do hunt as described. It is very effective as the prey can’t watch all of them at once and if one can blindside the prey, they have been successful.”

Robert Timm, retired director of University of California Hopland Research & Extension Center and a UC Cooperative Extension wildlife specialist, told me, “There are increasing numbers of reports of coyotes confronting or attacking people and pets (including at times dogs on leashes) from many areas throughout North America.  The experience of your reader is not atypical of what’s reported, particularly in areas where coyotes are now sufficiently habituated to humans to be living essentially full-time in suburbia or in natural areas frequented by tourists (e.g., state and national parks, campgrounds, hiking trails,) where coyotes likely come into contact with humans who have food… and probably intentionally feed coyotes in many instances, thereby increasing and speeding up the habituation process.  The reader didn’t mention the size or breed of the dogs involved; for medium to large dogs, such confrontations may be territorial defense, but for small to medium dogs I suspect the coyotes often regard the dogs (as at times they do toddlers and small children) as potential prey.”

Coyote pupDavid L. Bergman, Arizona State Director, USDA APHIS Wildlife Services, gave what seems like a reasonable explanation of what happened. “Based on the information provided I would consider that the coyotes were being territorial and protecting a den.  The owner’s dogs i.e., other canines, would be considered a threat to any new born pups in the den and thus a target for the territorial pack animals.  In Arizona, coyotes usually breed in February or March and have’a gestation period of 63 days. Birth of the pups could be during April or May right around when the individual had the encounter.  As to the pack size, it is likely that the pack was made up of the dominant male and female and last year’s pups that had not dispersed.  Pups disperse anywhere from 4 to 10 months of age with some dispersing after 1 year of age. As to the behavior of the attack, size will not matter when they are protecting pups.  From what is described, the coyotes showed their hand in that they were willing to protect their den site and they worked together to herd the intruders out of the area.”

The Experts’ Warning: All of the experts I consulted expressed the same concern that coyotes habituated to people can be dangerous, especially to pets and children. A paper co-authored by Robert Timm outlined a “sequence of increasingly bold coyote behaviors” by coyotes:

Nighttime coyote attacks on pets … sightings of coyotes in neighborhoods at night … sightings of coyotes in morning and evening … attacks on pets during daylight hours … attacks on pets on leashes and chasing of joggers and bicyclists … and finally, mid-day sightings of coyotes in and around children’s play areas. (From Timm et al 2004).

I tend toward tolerance and acceptance of wildlife, rather than aggression, but the experts agree that with coyotes this is a mistake. Human-coyote interactions have become more common across North America and attacks on pets and even people have grown sharply since the early 1970s. I believe our modern tendency to be friendly to wildlife is generally a good thing, but when applied to coyotes, it may be asking for trouble, putting people and pets at risk and leading ultimately to lethal control of coyotes when they cause problems. It’s not easy to re-instill a fear of humans in coyotes that have become habituated, so it’s better to keep them nervous from the start.

Coyotes start out wary of people, and the experts generally recommend yelling at them, throwing rocks at them, and otherwise harassing them to keep them wary. Don’t leave pet food outside, and take special care with children and small pets in areas where coyotes have been seen. Never feed coyotes.

Standing up to Aggressive Coyotes: The University of California has an excellent summary of information about human and coyote interactions. In it they suggest a strategy for standing up to a coyote. “If you or your pets are approached by an aggressive or fearless coyote, try to frighten it away by shouting in a deep voice, waving your arms, throwing objects at the animal, and looking it directly in the eyes. Stand up if you are seated. If you are wearing a coat or vest, spread it open like a cape so that you appear larger. Retreat from the situation by walking slowly backward so that you do not turn your back on the coyote.”

Given these suggestions, it sounds like Jessie did the right thing.

Sources:

Timm, R.T, Baker, R.O., Bennett, J.R., Coolahan, C.C. (2004). Coyote Attacks: An Increasing Suburban Problem. Proceedings of the Twenty-First Vertebrate Pest Conference (2004) (R.M. Timm and W.P. Gorenzel, Eds.), 47-57.  http://escholarship.org/uc/item/8qg662fb

Alexander, S.M. & Quinn, M. S. (2008) Human-coyote (Canis latrans) interaction in Canadian urban parks and green space: Preliminary findings from a media-content analysis. Contributed paper for the Canadian Parks for Tomorrow: 40th Anniversary Conference, May 8 to 11, 2008, University of Calgary, Calgary, AB.

Coyote. (03/2007) Retreived from http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn74135.html on 5/10/2016.

Photo Credits:

1. Manfred Werner (Tsui [de.wikipedia]) – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=41179

2. marya (emdot) from San Luis Obispo, USA (Flickr) [CC BY 2.0 (http://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons

3. By g’pa bill – “Mom, I’m Bored”…, CC BY-SA 2.0, https://commons.wikimedia.org/w/index.php?curid=22832514

Cite this article as: Pelletier, TC. (May 12, 2016). Why did these coyotes attack? Retrieved from http://askanaturalist.com/why-did-these-coyotes-attack/ on December 6, 2016.
Share:
  • Digg
  • Facebook
  • Twitter
  • Google Bookmarks
  • RSS
  • del.icio.us
  • Reddit
Print Friendly Print Friendly

Can animals evolve to be shape-shifters?

The Question: Hello, I can’t believe I’m even asking you this, but can an animal evolve shape-shifting abilities or is it completely fantasy?

Submitted by: Alexander, England

(click on photos and graphics to expand)

The Short Answer: Interesting question, Alexander, and thinking about this question just a couple days after Halloween seems appropriate. My first impulse was to say, “Of course not!” But then I started thinking a little more …

First, let’s decide what we’re talking about. In my less than extensive experience with science fiction and fantasy literature, it seems to me there are two basic types of shape-shifters. There are aliens who can take on the shapes of different animals. And there are aliens who can mimic humans, either generic people or specific people. I think we can agree that there are no animals that can do these things on earth presently … at least we don’t think so …

tadpole changing into a frog

frog metamorphosis

caterpillar turning into monarch butterfly

monarch metamorphosis

Which is not to say that there aren’t some impressive body transformations we know about. Think of a tadpole changing into a toad. Or a caterpillar changing into a monarch butterfly. In both cases, body shapes are changed and internal organs are rearranged. And if you didn’t know in advance, if someone handed you a fishlike, water-living tadpole and said it would change into a dry-land-living four-legged toad, you’d be pretty skeptical. If you didn’t know about the metamorphosis of insects, you might be even more skeptical if someone claimed a sluglike caterpillar had any connection whatsoever to the dainty, almost lighter-than-air monarch butterfly.

Maybe a little less dramatic is the transformation of a flounder fry, which starts out life as a tiny, but normal looking fish larvae before it turns into a flatfish. This involves a dramatic loss of symmetry, and the migration of an eye from one side of the head to the other. Pretty alien-ish. This video of a vertical flounder larvae turning into a flatfish shows the process. It was done by Dr. Alexander Schreiber, who studies vertebrate metamorphosis at St. Lawrence University.

There are also insects that can pull off the trick of pretending to be a creature other than what they are. For example, there are beetles, wasps, and others who camouflage themselves, visually and chemically, to infiltrate ant colonies. They even make the same sounds the ants do. They do it so well, the ants feed them and take care of them so the aliens can grow up and lay eggs and have even more alien imitators. And the ants never recognize they are being preyed on that way. Very sci-fi creepy.

All of these examples are fascinating, and an actual part of life here on Earth. But the transformations I mentioned aren’t really quite what we’re looking for. For one thing, they’re all uni-directional. Once a tadpole turns into a toad, it can’t revert to a tadpole. Same for the caterpillar and the flounder fry. And the creepy ant pretenders are fairly limited. Generally they can only imitate a single species and they’re stuck doing it for life.

But in any event, your question wasn’t really, “Does such a thing exist?” It was “Can it evolve?” Knowing what we know about evolution and natural selection on earth, could an animal (or a plant, I suppose) evolve the ability to imitate multiple species, and change back and forth at will?

It turns out that one animal actually does have those abilities, maybe not quite like a science fiction shape-shifter, but enough that, with another billion years of evolution, who knows?

I’m talking about the mimic octopus, Thaumoctopus mimicus, which is believed to have at least 15 targets in the repertoire of animals it can shape-shift into. To see a mimic octopus imitate a poisonous flounder or venomous lionfish or sea snake is impressive. Not quite at the level of a sci-fi or fantasy novel shape-shifter, but it successfully fools a lot of other animals, both predators and prey. It can change into these other animals repeatedly and reversibly.

It is the closest thing to a shape-shifter on earth. And who knows? Given another billion years of evolution, if there is an advantage to even more accurate mimicry, the mimic octopus might become better and better at its tricks until it truly qualifies as a shape-shifter.

So Alexander, if you’re wondering if there is a shape-shifter already on earth, I think the closest we have is the mimic octopus. If you’re wondering if something even more impressive could someday evolve, I guess I don’t see why not.

Cite this article as: Pelletier, TC. (November 3, 2015). Can animals evolve to be shape-shifters? Retrieved from http://askanaturalist.com/animals-evolve-to-shape-shifters/ on December 6, 2016.

Share:
  • Digg
  • Facebook
  • Twitter
  • Google Bookmarks
  • RSS
  • del.icio.us
  • Reddit
Print Friendly Print Friendly

What is this strange object floating in our lake?

strange object 1

strange object 1

The Question: On two different occasions we have retrieved similar strange objects floating in the lake we stay at in New Hampshire. I know it looks like it could be latex or some other man-made material-but it had a fleshy feel and no openings that could be seen. We did not cut it open. It had a bit of a fishy smell. It was about 13 cm (5 inches) and more like flesh than a plant. What are these?

strange object 2

strange object 2

Submitted by: Alison, New Hampshire, USA

(click on photos and graphics to expand)

The Short Answer: I didn’t recognize these UFOs (unidentified floating objects) right away, but I’m guessing there are some fishermen out there who would. When I started trying to imagine what kind of natural object from a northern lake would float, it suddenly occurred to me that the swim bladder of fish would qualify (also called air bladders or gas bladders).  Swim bladders are air filled sacks in the body that help a fish maintain neutral buoyancy in water.  Most of the large game fish Alison could find in a New Hampshire lake, such as bass or pike, have a swim bladder with a single bulb, but carp have a bladder that is in two parts, just like the ones Alison found.

My guess is that someone in Alison’s lake is catching fairly large carp, cleaning the fish by removing the internal organs, and dumping those organs in the lake. Most of the guts probably sink immediately and are eaten by scavengers. But the swim bladder, if it hadn’t been punctured, would float. And that’s what Alison found.

When I sent Alison a photo of the swim bladder of a carp, she immediately agreed it matched her UFOs.

carp anatomy

carp anatomy

Which came first, lungs or swim bladders? Anatomists long ago figured out that the lungs of some fish, the lungs of land vertebrates and the swim bladders of most fish are all homologous, meaning they develop in the same place in embryos as bulges on the pharynx, the tube that connects the mouth to the rest of the digestive system. That suggests that one of the organs evolved from the other, or they both evolved from the same earlier organ. Since we think of land vertebrates as “higher,” and more evolved organisms than fish, the natural assumption is that lungs evolved from swim bladders. In fact, Charles Darwin himself made that suggestion in On the Origin of Species.

But as evolutionary biologists looked deeper, it appeared that lungs may have come first in early fish that probably lived in shallow, oxygen deprived water. Because air holds far more oxygen than water, gulping air, as some fish do today, would have given these early fish the ability to survive in water with low oxygen. Over the generations, fish that had a pocket in the esophagus that held air did an even better job at gaining oxygen. Natural selection eventually led to fish that had actual lungs as modern lungfish do.  And all land vertebrates, from salamanders to people, are evolved from those early air breathing fish.

But that same apparatus that provided oxygen could also affect buoyancy, and for some fish, that may have proven to be even more useful than lungs because it would have allowed them to venture off the bottom of the ocean or river with minimal effort, opening up enormous expanses of water that had been a struggle to reach for fish that would otherwise sink. And over time, natural selection favored those fish with more and more effective swim bladders.

Further evolution of swim bladders led to the two main types. Fish like carp have a swim bladder that is still attached to the gut so that they are able to regulate the amount of air in the swim bladder by either gulping or burping/farting air. Turns out those cartoon pictures of goldfish blowing bubbles are somewhat accurate.  (Goldfish are in the same family as carp and have the same kind of swim bladder.)

Most fish, however, have swim bladders that are closed off. They fill the bladder by diffusing oxygen and other gasses from the blood into the air bladder, or absorbing them back into the blood. This system is less rapid than gulping, but it allows for the swim bladder to be regulated at any depth, without the need to surface. In fact, there are fish that can “pump” gasses into their swim bladders even against the enormous pressures of the deep ocean.

Sharks and rays, by the way, are part of a relatively small group of fish that don’t have swim bladders.

Swim Bladders and Beer: Commercial beer and wine manufactures often use a produce called isinglass to clarify their products. Because the yeast used to ferment beer and wine tend to float easily in water, particles of yeast can give the product a cloudy appearance. If you wait long enough, the yeast will fall to the bottom of the container, at which point, you can siphon off the clear liquid above. But long ago, brewers realized that certain types of natural collagens, the structural protein that makes up a large part of animal bodies, when mixed with newly made beer and wine, will cause the yeast to clump together and settle out more quickly, clarifying the beer or wine. The collagen you get when you process fish bladders, called isinglass, is especially good at this.

And fish bladders are a fairly cheap commodity, since there are enormous numbers of them that would otherwise be wasted when commercial fishing catches are cleaned. So the next time you drink a glass of beer or wine, remember the connection to Alison’s strange floating objects and wonder about the irony that an object designed by nature to float, does such a good job at making yeast sink.

(By the way, there is another use of the word “isinglass.” It can also mean sheets of the mineral mica.)

Sources: Thanks to Sarah Longo, a PhD candidate who studies fish evolution at the University of California, Davis, for her help.

Longo S., Riccio M., McCune A. R. 2013. Homology of lungs and gas bladders: Insights from arterial vasculature. JOURNAL OF MORPHOLOGY. Volume: 274. Issue: 6. Pages: 687-703.

Cite this article as: Pelletier, TC. (August 22, 2015). What is this strange object floating in our lake? Retrieved from http://askanaturalist.com/strange-object-floating-in-our-lake/ on December 6, 2016.

Share:
  • Digg
  • Facebook
  • Twitter
  • Google Bookmarks
  • RSS
  • del.icio.us
  • Reddit
Print Friendly Print Friendly

How fast do the tiny toads grow?

The Question: I work at a farm in northeast Pennsylvania. I read your article about toadlets. I have been enjoying seeing hundreds of these mini toads as I garden. Mine are still only about an inch long. How long does it take for them to reach full size?

Submitted by: Victoria, Pennsylvania, USA

(click on photos and graphics to expand)

The Short Answer: Victoria, glad to hear you are enjoying the toads. There are so many tiny toads all over my yard right now that I worry about inadvertently stepping on them. In northeastern Pennsylvania where you live, there are two toad species, the American toad (Anaxyrus americanus – formerly Bufo americanus) and the very similar Fowler’s toad (Anaxyrus fowleri – formerly Bufo fowleri). The easiest way to tell the two species apart is to flip them over and look at their bellies. If it has dark speckles, it’s probably an American toad and if not, it’s probably a Fowler’s toad.

toad-growth-chartBoth species start out as tiny toadlets, about 1 cm (3/8 inch) long. They grow rapidly in the first year and then slow down dramatically. By their second birthday, they are pretty close to full grown. Males generally begin to breed in their second year, females in their third. This chart is based on data for the American toad from Frogs of the U.S. and Canada by C. Kenneth Dodd. The book lists the size range of adult American toads as 5-9 cm (2-3.5 in.). The largest American toad on record was a whopping 15.5 cm (6.1 in.). Fowler’s toads are somewhat smaller at 4.5-8.2 cm (1.7-3.2 in.), with a record size of 9.2 cm (3.6 in.).

If your toadlets are already about an inch (2.5 cm), then they must have been early hatchers this year that have done very well eating small insects around your garden. Toads are pretty voracious insect eaters. One study estimated that an adult American toad could eat nearly 10,000 insects a year!

Sources: Dodd, C. (2013). Frogs of the United States and Canada. Baltimore: Johns Hopkins University Press.

Cite this article as: Pelletier, TC. (July 22, 2015). How fast do the tiny toads grow? Retrieved from http://askanaturalist.com/tiny-toad-growth/ on December 6, 2016.
Share:
  • Digg
  • Facebook
  • Twitter
  • Google Bookmarks
  • RSS
  • del.icio.us
  • Reddit
Print Friendly Print Friendly

What to do about this window dove nest?

sam's-doveQuestion #1: This bird made a nest next to my kitchen window. What kind of bird is this?

Submitted by: Samantha, New York City, New York USA

Question #2: A pair of mourning doves have made their nest on the outside windowsill of my home office on the 6th floor of an apartment building. At least one and possibly two fledglings are in the nest and are already trying their wings. I don’t want to harm the birds, but I want to remove the nest as soon as possible because it has infused my office with a barnyard smell. I have read that these birds can raise multiple broods in a season. Is there a time window for me to remove the nest and install a block to prevent their return?

Submitted by: Ron, New York City, New York USA

(click on photos and graphics to expand)

The Short Answer: These two reports of mourning doves (Zenaida macroura) nesting on window sills in New York City came within a week or so of each other. In one case, Sam and her small children were thrilled to have a bird nest so easily visible outside their window. In the other case, Ron was a little less happy, because the birds were nested right below his air conditioner, which was pulling in bird nest smell. Still, he was willing to wait till the dove chicks were free of the nest to remove it.

More Information: Like most species of the family Columbidae, mourning doves lay two eggs. They are remarkably flexible about where they will build their nest, sometimes choosing a low bush, and other times nesting 80 meters (260 feet) up in a tree. They’ll also nest on buildings, window ledges and even on the ground.

mourning-dove-chicksParents share incubation of the eggs, which hatch in 14-15 days. They also share feeding of the chicks with regurgitated “crop milk,” a liquid made from partially digested seeds. As the days go on, parents increasingly mix in seeds. The chicks are ready to leave the nest in about two weeks and after their first flight, and once they fledge they may return to the nest for a day or two, and then begin roosting in trees at night. For another two to four weeks the male parent will feed them until they are independent. Meanwhile, the female may begin laying new eggs.

Pairs can raise as many as six clutches in a single year, so Ron’s concern about his doves renesting under his air conditioner is a valid one. The U.S. Migratory Bird Treaty Act makes it illegal to tamper or move the nest of a native bird while it has eggs or chicks, however. So Ron’s best bet for a humane and legal solution is to watch for the baby birds to leave and then wait a day or two and remove the nest, hopefully before the female begins laying a whole new clutch.

Pigeon and doves: As I mentioned above, the family Columbidae includes doves and pigeons. In fact, there is no difference between the two from a taxonomic standpoint. Some members of the Columbidae are called doves and others are called pigeons, but that’s more about traditional names than anything scientific. In fact, our familiar city “pigeon” is also called both a “rock dove” and a “rock pigeon” (Columba livia).

Sources:

Otis, David L., John H. Schulz, David Miller, R. E. Mirarchi and T. S. Baskett. 2008. Mourning Dove (Zenaida macroura), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu/bna/species/117.

Share:
  • Digg
  • Facebook
  • Twitter
  • Google Bookmarks
  • RSS
  • del.icio.us
  • Reddit
Print Friendly Print Friendly