The Functions of Different Pupil Shapes

There are a lot of different pupil shapes among vertebrates (and some invertebrates, too).

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The eye itself is kind of a weird misshapen organ, particularly in land animals where it has had to compensate for, you know, the fact that it originally evolved in the water. Light passes differently through water than it does in air, not to mention that now we have to worry about our lenses- which have to be moist to properly function- drying out.

But the focus (ha ha) today is on the pupil, the transparent bit inside the iris that allows light to enter the eye. Without it, our eyes would be functionless. With it, there are a whole bunch of different ways that animals can shape their vision- and their pupil- to their advantage.

Of course, no two scientists seem to agree on exactly what these advantages are.

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The Pekapeka-tou-poto

Oh, sure, the Western scientific community calls this species the “New Zealand lesser short-tailed bat,” but I think we can all agree that the Māori name is much better, especially since you can then call it a pekapeka for short.

Pekapeka. God, I’m so happy.

Sadly this was the only creative commons image of the pekapeka I could find, so I'll ask you to use your imagination for the rest of the article.

Scientific name: Mystacina tuberculata. Sadly this was the only creative commons image of the pekapeka I could find, so I’ll ask you to use your imagination for the rest of the article.

Ok, so what’s there to distinguish the pekapeka from the hundreds and hundreds of other tiny insect-eating bats? Well, for starters, they’re one of only three mammal species native to New Zealand. Second, they spend roughly 30% of their foraging time not flying, but walking on the ground.

If that doesn’t sound impressive to you, you clearly don’t understand how much bats suck at walking. Imagine a seal, right? Sleek and beautiful under the water, pudgy-ground humping wobblers on land. Same deal for the bat, only replace the water with the air.

Essentially a bat. (Photo by Andreas Trepte.

Essentially a bat. (Photo by Andreas Trepte.)

True, there are a few other bat species that are also good at walking, most notably the common vampire bat, which can not only walk but hop and run. But in terms of phylogeny the vampire bat is like a million light years removed from the pekapeka, which is more closely related to the not-so-great-at-the-walking-thing ghost-faced and mustache bats. And unlike the vampire bat, which uses its walking as a stealth maneuver to sidle up to sleeping hosts and give ’em a lil love bite, the pekapeka doesn’t drink blood.

No, the pekapeka may spend time on the ground for other reasons entirely. Remember, it lives in New Zealand, where there are only two other species of mammals (both bats) and no snakes, which means there are next to no terrestrial predators. New Zealand is also home to a lot of birds… and a lot of flightless birds, like the kiwi.

Could the pekapeka be on its way to being the first species of flightless bat?

Well, not if we drive it to extinction first, but I’m getting ahead of myself here.

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Heterochrony: When Development Speeds Up or Slows Down

I’ve spoken of neoteny before in regards to domestic dogs- the concept that domestic dogs retain juvenile traits of their ancestral species, the gray wolf, into adulthood. These traits can include folded ears, shorter snouts, barking, more limited social behaviors, and a higher incidence of “puppyish” behaviors.

Photo on 2014-02-12 at 10.29 #2

For example, this dog is pestering me for attention right now.

But I think that while this concept isn’t new to those familiar with the evolution of the domestic dog, many people aren’t aware that there is an entire field of study devoted to examining the rates at which animals develop.

Let’s have a look!

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Introduction to Canidae


Pack of African wild dogs. (Photo by Bart Swanson.)

Canidae, otherwise known as the dog family, is one of the most highly adaptable carnivore families out there, with an array of body forms and behavioral adaptations. From the three-pound fennec fox to the gray wolf, which can weigh upwards of 130 pounds, there are 34 living species of canids.

I plan to do a series of individual articles on the behavior and life habits of different canids, but for now let’s have an overview of how the group evolved and what sets them apart from other carnivorous mammals.

I’ll also discuss- briefly- the misconceptions of canid social behavior present in popular media.

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Introduction to Chiroptera


I don’t know if you guys have noticed this, but I’m a pretty big fan of bats. I’ve been meaning to do a grand ole post on them for a while, and this seems to be the perfect season to do it. So I’d like to talk briefly about the incredible diversity within order Chiroptera.

QUICK BAT FACTS! Did you know….

  • Bats comprise about one-fifth of known mammal species?
  • The smallest known mammal is a bat? (Well, there’s also a shrew contender, but we’re going with the bat today.)
  • The largest bats have five-foot wingspans?
  • Tequila wouldn’t exist without bats? (One species pollinates the agave plant it’s made from.)
  • Some bats have nipples in their armpits?
  • NO bat species is blind?
  • Bats can live over 20 years?
  • Bats are highly intelligent, social animals?

Okay, let’s learn about bats.

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Can Animals Have Pets?

This is definitely a really interesting topic to me, and I’ll try to answer to the best of my ability. Keep in mind that I’m coming at this from a psychology/biology background, not an anthropological one- I’d love to hear people from that field weigh in on the topic.

I’d also like to note that some of the things in this article aren’t based on scientific research but my own observations and opinion.

Here’s what I go over:

  • Why people keep animals, and the types of relationships people have with animals
  • Domestic vs tamed animals
  • Conditions that allow humans to keep pets
  • Animal-animal relationships that resemble human pet keeping

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Chase-Away Sexual Selection

What is chase-away selection?

In preparation for answering this question I dipped my toes back into the cesspool of sexual selection theories and MAN is it just a hot sweaty mess. Utterly fascinating, of course, but just a mess.

Ok, so chase-away selection theory. To understand where it comes from, you’ve got to understand a few basic things about sexual selection itself.

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