What we still don’t know
Weather.com says it’s a whopping 6 degrees outside right now, but that it feels like -14. I am really wishing I were back at the conference in California right now…
By now, both Meredith and I have gushed about all the “bio-celebrities” at the Gordon Research Conference on Predator Prey Interactions. How we got to come face to face with the scientists whose work we’ve read, memorized, admired for years. But what I think has been an even more exciting outcome of this research conference than getting to hang out with our scientific heros and listen awe-struck about everything they’ve done in the past that has led to their fame today, was a chance to sit down with them over a beer or glass of overpriced red, and talk about the future. Not just where our various and varied subfields have been, and not even just where they are going, but where they need to go. Where the holes are in our knowledge, and what we need to do to fill them.
Much of ecology is about developing “predictive capacity.” The ability to not just describe the patterns we see in the world about us, but the ability to predict what will happen when things change. Understanding how climate change affects annual bird migrations, for example, or what losing species means for the spread of disease. We develop conceptual frameworks to tie together outcomes from different experiments and scattered observations drawn from ecosystems around the world, and these frameworks give us a way to articulate our expectations about 1) what underlying processes we think are driving the dynamics of a system and 2) a way to test those hypotheses: do the outcomes match what we predicted would happen? Or is something else going on that we need to investigate further?
One of the things I slowly worked up the courage to articulate at the conference was that I think that science surrounding predator-predator dynamics really lacks this sort of integrated, synthetic, predictive framework. We draw on a whole bunch of different sets of theories to understand the patterns of suppression and coexistence apparent in apex-mesopredator (top- and middle- predator) systems. There’s a ton of theory out there on how species coexist when they eat the same thing, or how they coexist when they eat the same thing and also eat each other. There’s a lot of theory on how predators coexist with the things they eat. There are predictions for when we expect to see species able to coexist, when we don’t, and how these different outcomes change from, say, low productivity tundra to high productivity rainforests.
But around the world, top predators suppress populations of smaller predators (called mesopredator suppression). It’s not because the top predators are eating up all the food, and it’s not because the top predators are eating the mesopredators. It seems to happen because the bigger guys chase, harass, and kill the smaller guys. This is bad enough, but it also creates a “landscape of fear” in which that the smaller guys change their behaviors to try and avoid these aggressive encounters. There are lots and lots of ways in which mesopredator suppression can happen…but we (as a community of ecologists) don’t have a good, integrated framework for making predictions about when we expect to see mesopredator suppression vs. when we don’t. We don’t have a set of expectations about how these patterns change with different behaviors or different types of environments. We don’t have a solid understanding of what mesopredator suppression means for other small predators, prey animals, and the plants that the prey animals eat. We have lots and lots of examples of all sorts of complex things happening…but we don’t yet have the ability to predict how these things play out in new systems.
And that, to me, is one of the most exciting “holes” that needs filling. How do we tie together our knowledge from all of these disparate studies, where lions suppress wild dogs but not cheetahs, or coyotes kill foxes left and right but aren’t actually the reason that fox populations are low. I guess my PhD is trying to fill a tiny, tiny bit of that hole. But it’s a damn big hole and sometimes it’s hard to see how one PhD will cover a whole lot of ground. I guess what was so exciting at the GRC is just how many other people are also trying to fill those holes…and with all of us working together, we just might actually be able to understand the world around us that much better.