Tuesday, October 16, 2018

The Smell of Fear

A repost of an original article from October 24, 2012.

Several animals, many of them insects, crustaceans and fish, can smell when their fellow peers are scared. A kind of superpower for superwimps, this is an especially useful ability for prey species. An animal that can smell that its neighbor is scared is more likely to be able to avoid predators it hasn’t detected yet.

Who can smell when you're scared? Photo provided by Freedigitalphotos.net.

“What does fear smell like?” you ask. Pee, of course.

I mean, that has to be the answer, right? It only makes sense that the smell of someone who has had the piss scared out of them is, well… piss. But do animals use that as a cue that a predator may be lurking?

Canadian researchers Grant Brown, Christopher Jackson, Patrick Malka, Élisa Jaques, and Marc-Andre Couturier at Concordia University set out to test whether prey fish species use urea, a component of fish pee, as a warning signal.

A convict cichlid in wide-eyed
terror... Okay, fine. They're
always wide-eyed. Photo by
Dean Pemberton at Wikimedia.

First, the researchers tested the responses of convict cichlids and rainbow trout, two freshwater prey fish species, to water from tanks of fish that had been spooked by a fake predator model and to water from tanks of fish that were calm and relaxed. They found that when these fish were exposed to water from spooked fish, they behaved as if they were spooked too (they stopped feeding and moving). But when they were exposed to water from relaxed fish, they fed and moved around normally. Something in the water that the spooked fish were in was making the new fish act scared!

To find out if the fish may be responding to urea, they put one of three different concentrations of urea or just plain water into the tanks of cichlids and trout. The cichlids responded to all three doses of urea, but not the plain water, with a fear response (they stopped feeding and moving again). The trout acted fearfully when the two highest doses of urea, but not the lowest urea dose or plain water, were put in their tank. Urea seems to send a smelly signal to these prey fish to “Sit tight – Something scary this way comes”. And the more urea in the water, the scarier!

But wait a minute: Does this mean that every time a fish takes a wiz, all his buddies run and hide? That would be ridiculous. Not only do freshwater fish pee a LOT, many are also regularly releasing urea through their gills (I know, gross, right? But not nearly as gross as the fact that many cigarette companies add urea to cigarettes to add flavor).

The researchers figured that background levels of urea in the water are inevitable and should reduce fishes fear responses to urea. They put cichlids and trout in tanks with water that either had a low level of urea, a high level of urea, or no urea at all. Then they waited 30 minutes, which was enough time for the fish to calm down, move around and eat normally. Then they added an additional pulse of water, a medium dose of urea, or a high dose of urea. Generally, the more urea the fish were exposed to for the 30 minute period, the less responsive they were to the pulse of urea. Just like the scientists predicted.

A rainbow trout smells its surroundings.
Photo at Wikimedia taken by Ken Hammond at the USDA.

But we still don’t know exactly what this means. Maybe the initial dose of urea makes the fish hide at first, but later realize that there was no predator and decide to eat. Then the second pulse of urea may be seen by the fish as “crying wolf”. Alternatively, maybe the presence of urea already in the water masks the fishes’ ability to detect the second urea pulse. Or maybe both explanations are true.

Urea, which is only a small component of freshwater fish urine, is not the whole story. Urea and possibly stress hormones make up what scientists refer to as disturbance cues. Steroid hormones that are involved in stress and sexual behaviors play a role in sending smelly signals in a number of species, so it makes sense that stress hormones may be part of this fearful fish smell. But fish also rely on damage-released alarm cues and the odor of their predators to know that a predator may be near. Scientists are just starting to get a whiff of what makes up the smell of fear.

Want to know more? Check these out:

1. Brown, G.E., Jackson, C.D., Malka, P.H., Jacques, É., & Couturier, M-A. (2012). Disturbance cues in freshwater prey fishes: Does urea function as an ‘early warning cue’ in juvenile convict cichlids and rainbow trout? Current Zoology, 58 (2), 250-259

2. Chivers, D.P., Brown, G.E. & Ferrari, M.C.O. (2012). Evolution of fish alarm substances. In: Chemical Ecology in Aquatic Systems. C. Brömark and L.-A. Hansson (eds). pp 127-139. Oxford University Press, Oxford.

3. Brown, G.E., Ferrari, M.C.O. & Chivers, D.P. (2011). Learning about danger: chemical alarm cues and threat-sensitive assessment of predation risk by fishes. In: Fish Cognition and Behaviour, 2nd ed. C. Brown, K.N. Laland and J. Krause (eds). pp. 59-80, Blackwell, London.

Tuesday, October 9, 2018

Caught in My Web: Mind-Altering Substances

Image by Luc Viatour at Wikimedia Commons
Drunken birds have gone viral this week! For this edition of Caught in My Web, we wonder if animals alter their mental states like people do.

1. Drunk Minnesotan birds are flying into windows! At least that is what the viral story says. But the truth may be a bit more measured. As the Police Chief of Gilbert, Minnesota says, “It sounds like every bird in our town is hammered, and that’s not the case.” Read the real story here.

2. But do wild animals really drink alcohol? Not in the way that we do, maybe, but many consume overly fermented fruits. Some have developed a tolerance to the high alcohol content, others, not so much. Just ask this poor drunk moose that got herself stuck in a tree after eating too many fermented apples.

3. But it’s not just fermented fruits that get animals drunk. Some fish can make their own alcohol to help them survive a long winter under the ice.

4. What about the effects of other mind-altering substances on animals? Ever wonder what kind of web a spider would make on different drugs? In 1948, a zoologist at the University of Tubingen in Germany by the name of H.M. Peters did.



5. Octopuses are normally very solitary creatures… that is, unless they are given ecstasy. Apparently, even octopuses seek social interactions when they take the common party drug.

Tuesday, October 2, 2018

Friends Without Benefits: A Guest Post

A reposting of an original article by Joseph McDonald

Do you want to avoid the friend zone?
Photo by freedigitalphotos.net.
Guys DREAD the friend zone. That heart-aching moment when the girl you’ve been fawning over for years says you’re the best listener, the sister she never had, or so much better than a diary! You’ve been so nice to her and her friends, listening to all their drama. But that’s just the problem... you’re too nice to too many people.

Research performed by Aaron Lukaszewski and Jim Roney at the University of California – Santa Barbara (UCSB) tested whether preferences for personality traits were dependent on who the target was. In Experiment 1, they asked UCSB undergrads, on a scale from 1 to 7, the degree to which their ideal partner would display certain traits towards them and towards others. These traits included synonyms for kindness (e.g. affectionate, considerate, generous, etc.), trustworthiness (committed, dependable, devoted, etc.), and dominance (aggressive, brave, bold, etc.). Experiment 2 replicated the procedures of Experiment 1. The only difference was that the term “others” was divided into subsets including unspecified, family/friends, opposite sex non-family/friend, and same-sex non-family/friend.

Let’s go over the do’s and don’ts so that future “nice guys” aren’t friend zoned. According to the findings, as graphed below:

Figure from Aaron and Jim's 2010 Evolution and Human Behavior paper.
1. Women generally prefer men who are kind and trustworthy. So, to get that girl, don’t be mean; that’s not the point. This isn’t 3rd grade so don’t pull her hair and expect her to know that you LIKE-like her.

2. Women prefer men who are kinder and more trustworthy towards them than anyone else. So it’s not so much whether you are nice enough, its whether she knows you are nicer to her than anyone else.

3. Women prefer men who display similar amounts of dominance as they do kindness. Dominance isn’t a bad thing, as long as you can distinguish her friends from her foes; especially her male friends.

4. To make things more complicated, women also prefer men who are directly dominant toward other men but don’t display dominance toward them or their family/friends, whether male or female. Some guys may want to befriend these other men, but be weary. Women preferred dominance over kindness in this situation, so kindness may not be enough.

These preferences may have developed to avoid mating with someone willing to expend physical and material resources for extramarital relationships, and invest greater in her and the children. Moderate kindness and trustworthiness toward others will maintain social relationships and prevent detrimental relationships, which may be why women generally prefer kind and trustworthy guys. But in all fairness, women can be in the friend zone too; just look at Deenah and Vinny (excuse the shameful Jersey Shore reference).

There are some things that guys look for in a mate, so ladies, here is a little advice:

1. Guys generally want a mate who is kind and trustworthy, too. We’re not that different; so don’t act a little crazy because you think he likes it. He doesn’t.

2. Guys also prefer women who display dominance toward other women (non- family/friend). Don’t be afraid to put that random girl with the prying eyes in her place.

Contrary to the hypotheses predicting female mate preferences, male mate preferences may have developed as a way to take advantage of strong female-based social hierarchies. No matter what the reasoning, however, if you can
1) be kinder and more trustworthy towards that special someone than anyone else and
2) display dominance over other same-sex people, then feel free to say good-bye to the friend zone!


For further details, check out the original experiment:

Lukaszewski, A., & Roney, J. (2010). Kind toward whom? Mate preferences for personality traits are target specific Evolution and Human Behavior, 31 (1), 29-38 DOI: 10.1016/j.evolhumbehav.2009.06.008