Tag Archives: nature

My spot, your spot.

I grew up on an island with seven million other people. Let’s just say it was difficult to find a spot to call your own. One day, as a youngin’ exploring the world on my bike, I broke off a path that ran along Sunrise highway and continued on down a hiking trail that snaked along a waterway in the local state park. I eventually came to a small clearing, sat down, and heard the weirdest thing. Nobody. No cars, no lawnmowers, no people. Just the birds and the chipmunks and the occasional splash of a fish.

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I felt as if I had stumbled on secret treasure. I spent a lot of time at this spot over my formative years, reading and thinking and being alone with my little patch of Long Island wilderness.

Before I left town for college I carved a “V” into the tree next to the water and said goodbye. While at college, I decided to major in biology, a decision shaped by my time out in the woods watching nature. I even wrote an essay about this spot for my freshmen writing class.

That biology major took on a life of its own, turning into an adventure through states, labs, and disciplines, and eventually resulting in a PhD from a zoology department and a dissertation on cancer and aging.
Last weekend Begum and I were visiting my parents and we decided to go for a quick hike before the ferry back to CT. A rush of memories came back, and I ran along this trail explaining my spot to her. She eventually found the V for me.

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Both of these images are from June 2017

It was the first time in over a decade that I set foot in this clearing. Needless to say, it was a powerful experience, and it sparked a bout of retrospection that, thankfully, I have been happy to ride.
I said a thank you, and another goodbye, and we ran to catch our ferry.

This summer, I hope you go out and explore, and find your own spot.

Will the real Banana Spider please stand up?

I’ve encountered two different species of giant (subjective classification based on my previous New-York-State-only spider exposure) orb weaver spiders while living in Gainesville (and one non-orb weaver!). Both of which have been referred to as a ‘banana spider’. So, who are these spiders anyway, and which one is really the true banana spider?

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Exhibit A- picture taken at the La Chua trail.

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Exhibit B- picture taken in my front yard. (notice the flash reflection in the front eyes!)

It turns out that there are a few spiders referred to as a banana spider. However, only one of those spiders is pictured above, and it’s Exhibit B- the Golden Orb-Weaver (Nephila clavipes). Exhibit A, with its characteristic zigzag web, is commonly referred to as the Yellow Garden Spider (Argiope aurantia).

Apparently the Golden Orb-Weaver was recently moved out of the Orb-Weaver family and placed in the Nephilidae family because their webs weren’t sophisticated enough. Bummer!

Regardless of species name and web sophistication, if there’s one thing I’ve learned while living in Florida, it’s watch where you walk…

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Banana spider waiting to catch a low flying plane

 

Awesome camouflage

Staying in the lab is tough when you live in the sunshine state. I mean, at SUNY Geneseo it was easier- the lab served as a warm refuge against those Western NY winds and clouds. So every once and again I’ll find a break in the Floridian sunshowers and bring my work outside. However, as any biologist can tell you, work is impossible outside because you always get distracted by some cool critter crawling by your laptop. Case in point: last time I tried this I noticed a little pile of moss moving across the table…

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… so of course I flipped it over…

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…and found legs! (Woah, I need to find out what this is.) Further investigation revealed impressive mandibles and a set of sticky spines:

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It looked very similar to an antlion, which is the larval form of a certain family of lacewing. Antlions are awesome in their own right, they form little trenches in the sand and eat ants that fall into their trap. I teach an intro bio lab on the spatial distribution of organisms, and I always take the students outside to hunt for antlions (they are typically (spoiler) clumped together in sandy spots under the eaves of buildings). And I always show this video:

Anyway, it turns out that critter I found was also a larval lacewing! Certain species have sticky spines on their back that trap debris and help the larva blend in with their environment. This isn’t a new tactic- scientists have found a 110 million year old larval lacewing trapped in amber that has fern trichomes stuck on its back. How cool is that?! (Another spoiler: very)

And such is the curse of the biologist- go outside to write and in minutes you are a few Wikipedia pages deep classifying insects.

1.1 Billion

That’s the number of heartbeats in every animal’s lifetime*. Don’t believe me?

Let’s consider an extreme comparison. A mouse can live for 3 years, and has a heartbeat of about 670 beats per minute. There are 525600 minutes in a year (365 days/year * 24 hours/day * 60 minutes/hour). So, that’s 3 years/lifetime *525600 minutes per year * 670 beats/minute ≈ 1.1 billion beats/lifetime. What about an elephant? They can live up to 70 years and have a heartbeat of about 30 beats/minute. 70 years/lifetime * 525600 minutes/year * 30 beats/minute ≈ 1.1 billion beats/lifetime. Woah… what?!

Ok, ok… you probably noticed that those “equals” signs are actually squiggly “approximately” signs, and if you did the math (you should!) you would see that they are both a little off from exactly 1.1 billion. But still, they are damn close. What gives? Why would the number of heartbeats be an invariant property of the animal kingdom? Let’s dive a little deeper.

The answer lies in allometric scaling, or how different properties of life scale with the body mass of organisms. It turns out that the power (energy per time, metabolism) required to support a given unit of mass of an organism scales with the mass of that organism to the (-1/4) power- meaning that smaller organisms use energy at a faster rate per unit mass than larger organisms. Other rates, such as breathing rate and heartbeat rate, also scale with bodymass^(-1/4). Lifespan, on the other hand, has been shown to scale with bodymass^(1/4). If you want to find how the lifetime total beats scale, you can multiply those two together (beats/time * time = beats). Bodymass^(-1/4) * Bodymass^(1/4) = Bodymass^0, which is always 1, meaning that the total beats is invariant of bodymass! More on allometry and metabolism in later posts. And maybe I’ll learn how to show equations in wordpress someday.

This paper (which probably takes into account more than the 2 points I used above) cites the total number of heartbeats in an animals lifetime as 1.5 billion.

Now, given this number, can we backtrack and use the relationship to see how long humans are predicted to live? Given a certain heart-rate, how long would it take us to use up our 1.5 billion?

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R code:
curve(1.5e9/(x*525600), xlim=c(40,100), lwd=5,
ylab=”Lifetime (years)”, xlab=”beats/minute”);
abline(v=60, col=”red”);abline(v=70, col=”red”)

If an animal beats its heart between 60 and 70 times a minute, it would use up its 1.5 billion beats in around 40-45 years. Is this a ballpark estimate of a human’s lifetime in the wild? (Aside: if you take the 1.1 billion heart beats derived from mice and elephants and assume a heart-rate of 70 beats per minute for humans you get 29.9 years!)

Now, don’t worry. Humans have found amazing ways to increase their lifespan, and it’s not like everyone has a set number of heart beats to get through before it’s all over. This is just an interesting result of looking at metabolism and ecology – and what’s even more interesting is looking at the animals that stray from the predictions.

*That’s about the predicted number of heartbeats in an average organism’s lifetime

Flocking Science

Check out the beautiful video below of a “murmuration” (flock) of starlings acting in hypnotic unison:

Now, if you spend all day thinking about how to model biological systems (who doesn’t?), you might see that video and wonder about the rules each bird must follow to allow such spectacular emergent dynamics. Every individual bird probably gets some simple cues (direction, speed) from its neighbors, who get some from their neighbors (and that first bird), etc etc, and when these simple cues are acted upon and combined together all the birds form a giant complex morphing swarm.

A quick search reveals that the starling dynamics, and swarming behavior in general, have been the focus of a considerable amount of research and modeling. I’ll link this PLoS ONE paper since it’s open access (meaning everyone can view it in its entirety for free) and has some really cool videos showing off the modeling endeavors of the authors. In their simulation, each individual is characterized by parameters like mass, speed, position, and orientation- and these parameters get updated based on interactions with other individuals within a certain neighborhood. Just like in real life, these simple interactions scale up to show a swarm of individuals that behave as a complex, yet unified, group. (check out the videos in the link!)

I’ll also share this PLoS Computational Biology paper (also open access) which explores why individual starlings pay attention and respond to exactly seven of their neighbors (the authors report the number is special because it optimizes the balance between group cohesiveness and individual effort).

Another side effect of thinking about biology all day is always having to ask “Why (and how) did this evolve?” That is, what benefit does this intricate dance give the birds that allowed it to selected for and maintained? Being relatively ignorant of birds and their behaviors, it seems that such a show would turn into a buffet for predators. Well, maybe not. Here is a video of a Peregrine Falcon trying to snatch a starling during the flocking behavior and continually coming up empty handed (clawed?). The Peregrine Falcon is the fastest member of the animal kingdom, reaching diving speeds of over 200mph, so maybe this dizzying behavior is a great way to confuse even the quickest of predators.

I’m sure there is more to it than just predator avoidance, so feel free to add your 2 cents below!

Cuban Treefrog (Osteopilus septentrionalis)

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I am pretty sure this is a Cuban Treefrog, although please tell me if I’m wrong!

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I let it go outside (sorry native frogs :-/). Anyway, it was definitely a neat surprise to find inside! That is, if you aren’t native to Florida yourself.

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Carolina Wolf Spider

Carolina Wolf Spider

Hogna carolinensis, found in my apartment, Gainesville, FL.