Great Plains Anywhere: John DeLong on Predators

Center for Great Plains Studies Author

03/12/2024 Added

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In this episode, we talk with Dr. John DeLong about his work studying predator-prey interactions and climate adaptation, tracking how both adapt and evolve to better fit their surroundings, from the smallest microscopic creatures to large birds of prey. Dr. DeLong is an Associate Professor of Biological Sciences at the University of Nebraska-Lincoln and is also the Director of the university's Cedar Point Biological Station.

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[00:00:00.150]Welcome to "Great Plains Anywhere,"
[00:00:02.040]a Paul A. Olson lecture
[00:00:03.750]from the Center for Great Plains Studies
[00:00:05.430]at the University of Nebraska.
[00:00:07.270](gentle guitar music)
[00:00:08.430]In this episode,
[00:00:09.300]we talk with Dr. John DeLong
[00:00:10.950]about his work studying predator-prey interactions
[00:00:13.830]and climate adaptation,
[00:00:15.600]tracking how both adapt and evolve
[00:00:17.580]to better fit their surroundings,
[00:00:19.140]from the smallest, microscopic creatures
[00:00:21.270]to large birds of prey.
[00:00:23.370]Dr. DeLong is an Associate Professor of Biological Sciences
[00:00:26.700]at the University of Nebraska-Lincoln,
[00:00:28.890]and is also the Director
[00:00:30.090]of the university's Cedar Point Biological Station.
[00:00:33.960]The University of Nebraska is a land-grant institution
[00:00:37.020]with campuses and programs
[00:00:38.760]on the past, present, and future homelands
[00:00:41.430]of the Pawnee, Ponca, Otoe-Missouria, Omaha,
[00:00:45.360]Dakota, Lakota, Kaw, Cheyenne, and Arapaho peoples,
[00:00:49.920]as well as those of the relocated Ho-Chunk, Sac and Fox,
[00:00:53.460]and Iowa peoples.
[00:00:55.140]I'm an evolutionary ecologist,
[00:00:57.060]and I focus mostly on predator-prey interactions
[00:01:00.030]and climate adaptation, and whenever possible,
[00:01:03.810]the intersection of the two,
[00:01:05.280]how predator-prey interactions are modified
[00:01:09.120]by things like temperature or other environmental changes,
[00:01:12.636]and whether or not those things can adapt, right,
[00:01:15.570]where a population or species can adapt or evolve
[00:01:17.940]in response to the stressor of warmer temperatures
[00:01:20.850]or more extreme climates.
[00:01:22.860]Adaptation is a big part of that, right,
[00:01:24.480]where we have some sort of landscape ecology,
[00:01:29.190]species interactions, competitors, predators,
[00:01:32.280]things you need to eat, right,
[00:01:34.200]all these ecological interactions.
[00:01:35.850]And then somehow,
[00:01:36.683]evolution is acting on all these interactions,
[00:01:41.010]being driven by them, because they determine your fitness,
[00:01:45.300]whether or not you can grow and have babies or survive.
[00:01:48.570]Predators are everywhere.
[00:01:49.890]They come in all sorts of forms, right.
[00:01:51.960]I mean, nearly everything that isn't a plant or a parasite
[00:01:59.610]is trying to acquire its energy from something else, right.
[00:02:07.980]You have predators that are single-celled organisms,
[00:02:10.410]like proteus, the paramecia we work on.
[00:02:12.090]They are predators of bacteria and algae, right,
[00:02:15.690]and then things that eat them,
[00:02:17.460]all sorts of crustaceans or small insects
[00:02:21.030]and things can eat them, predators,
[00:02:24.570]other sort of macro invertebrates,
[00:02:26.940]and little tiny fish, all the way up.
[00:02:28.800]Most fish are predators.
[00:02:30.690]Some eat plants, or coral, or things like that,
[00:02:34.140]but most of the birds are predators.
[00:02:39.270]Spiders, just kinda go on, and on, and on, right,
[00:02:43.410]like, the tapestry, the food web, right.
[00:02:48.030]All of the stuff out there, if it's an animal,
[00:02:50.670]it's probably runnin' around looking for something to eat.
[00:02:52.500]Now, of course, there are plenty of herbivores out there,
[00:02:56.760]some of which aren't as strictly herbivorous
[00:02:59.160]as you might think, right.
[00:03:01.230]But most of them have predators,
[00:03:03.420]so that you've got your large carnivores as well, right.
[00:03:08.220]Just, they really are truly surrounded by predators,
[00:03:11.340]and they all, with their own sort of version of that, right.
[00:03:16.590]Even if many of the birds might eat berries
[00:03:20.040]during the winter or during migration,
[00:03:21.660]when it comes time to breed,
[00:03:23.460]then they might switch over to eating insects
[00:03:26.430]and feed their babies with insects,
[00:03:27.750]so kind of go back and forth mixotrophs, right.
[00:03:32.700]So usually when people think about predators,
[00:03:34.500]they do think lions and tigers and large carnivores
[00:03:40.170]of some sort, right.
[00:03:41.490]When I think about predators,
[00:03:42.600]I think about them and I think about everybody else, right,
[00:03:47.010]everything from tigers to ciliates.
[00:03:50.670]So the effect of predators is everywhere,
[00:03:52.830]and it's all very layered, right.
[00:03:55.950]So your Great Horned Owl might eat a squirrel
[00:04:00.210]that ate bird eggs and the birds ate insects,
[00:04:04.710]and they may have eaten insects or spiders
[00:04:07.290]that ate insects that ate spiders and insects,
[00:04:10.320]all the way down to plants, right.
[00:04:12.570]So there may be many, many layers and steps
[00:04:15.120]between even our local big predators,
[00:04:19.740]like Great Horned Owls, and even in the city.
[00:04:23.880]And so this gets magnified,
[00:04:26.160]the more kinds of species you have
[00:04:28.140]and the more kinds of habitats you have.
[00:04:29.910]Cedar Point, right, is it's not unique,
[00:04:33.390]but it's special in that
[00:04:34.830]many of the lakeside terrestrial species are eating things
[00:04:39.240]that have emerged out of the water.
[00:04:41.400]So they have these extra long trophic chains, food chains,
[00:04:46.050]because there was a whole food chain
[00:04:48.630]that produced the emerging insects,
[00:04:51.540]who then get eaten by spiders
[00:04:53.580]and then get eaten by other spiders,
[00:04:55.320]but then get eaten by birds
[00:04:56.520]that get eaten by other birds, right.
[00:04:58.590]So, it's really long and very interwoven, right,
[00:05:05.160]and so much of what ecologists call
[00:05:09.240]the stability of a natural system comes from having
[00:05:12.780]these really highly distributed predator-prey interactions,
[00:05:15.960]where if you have a super strong predator-prey interaction,
[00:05:19.620]you have more potential to over exploit something, right.
[00:05:23.310]And so, they tend to move around more.
[00:05:26.670]I mean, their populations tend
[00:05:27.870]to decline quickly and grow quickly
[00:05:30.480]because you can over exploit.
[00:05:31.890]But if you spread things out,
[00:05:35.160]they tend to be buffered
[00:05:37.290]against these sort of over exploitive effects,
[00:05:41.310]and so it's often thought that
[00:05:44.040]one of the roles of predators, generally,
[00:05:46.740]in the Great Plains and everywhere else,
[00:05:48.240]is that they have a stabilizing effect,
[00:05:51.930]which can allow more species to persist in the same places.
[00:05:55.860]So they can enhance diversity by,
[00:05:59.550]maybe inadvertently or just by chance,
[00:06:02.910]eating the most common things,
[00:06:04.440]making more room for other stuff.
[00:06:06.210]That's a famous effect called keystone predation, right,
[00:06:11.670]but then when you start pulling those predators
[00:06:13.410]out of the system, right,
[00:06:15.600]the stabilizing effects of keystone predators
[00:06:18.510]or the trophic effects
[00:06:20.850]of having top things eating lower things
[00:06:23.220]start to move around.
[00:06:24.930]And that allows species to, populations to grow,
[00:06:28.380]that weren't growing like they were before,
[00:06:31.800]and so one of the kind of classic examples of this
[00:06:36.900]is a meso predator release,
[00:06:40.020]where humans don't really want to be near
[00:06:43.980]mountain lions and wolves all the time.
[00:06:49.380]Certainly can be at risk from them,
[00:06:52.500]so if we remove those from the system, right,
[00:06:55.530]the things that those predators were eating will grow.
[00:06:59.550]And those predators were eating deer or raccoons
[00:07:03.960]or all these other things that are
[00:07:06.000]like a 10th of the size that they were,
[00:07:08.190]or in the case of wolves, their size or larger.
[00:07:12.600]But they get a little release,
[00:07:15.150]and so we see lots of extra deer and lots of extra raccoons
[00:07:18.630]and things like that.
[00:07:21.469]And so the removal of predators has a noticeable effect
[00:07:25.950]on the system that remains,
[00:07:29.190]and that's called a trophic cascade.
[00:07:30.600]So then you have more deer, and then they eat more plants,
[00:07:33.510]and so the plants can go down and so on.
[00:07:36.510]In the case of raccoons, you have more raccoons,
[00:07:38.940]they eat more bird eggs, and the birds go down,
[00:07:41.460]and then the insects come up, right.
[00:07:43.320]So you have all of these sort of knock-on effects,
[00:07:46.530]and those are what people will call
[00:07:49.050]an indirect effect, right.
[00:07:50.670]So you think, oh, I'm just gonna remove these wolves
[00:07:53.250]and then everything will be utopia,
[00:07:55.680]and then everything kinda starts goin' haywire.
[00:07:58.260]Of course, eventually in the long term,
[00:08:00.630]they kinda settle out in some new place,
[00:08:02.850]and it may or may not be a place that humans like,
[00:08:05.490]and then they would wanna go in and manage it more.
[00:08:08.430]One of the things I learned
[00:08:10.056]and am excited about in predator ecology
[00:08:12.930]is the role predators can play in biocontrol, right,
[00:08:17.280]so it's quite important globally that we can use predators,
[00:08:22.350]including spiders, to control agricultural pests.
[00:08:25.470]So if you can find the right predator
[00:08:27.120]that really likes to eat your aphid
[00:08:29.130]or your white fly or something like that,
[00:08:31.500]you can kinda try to foster the support of those predators.
[00:08:35.700]And then you have this predator-prey interaction
[00:08:37.560]that's really widespread and playing a huge role
[00:08:41.400]in facilitating more productive agriculture
[00:08:45.480]without necessarily having to spray pesticides.
[00:08:48.270]With climate change, right,
[00:08:49.920]most of the predators we're talkin' about are ectotherms,
[00:08:53.640]that they respond,
[00:08:54.510]their body temperature is responding
[00:08:57.270]to the environmental temperature, unlike your wolves,
[00:08:59.850]who are regulating their temperature internally.
[00:09:03.060]So their predator-prey interaction, like how fast they move,
[00:09:07.560]how fast their prey moves,
[00:09:08.940]and their ability to digest,
[00:09:10.380]are all very temperature dependent.
[00:09:12.240]And so their ability to do these jobs,
[00:09:14.550]like control aphids or just function in a natural system,
[00:09:19.830]becomes very temperature dependent.
[00:09:21.930]And we've been really keen
[00:09:23.610]to try to measure those temperature dependencies
[00:09:27.030]and get our minds around like,
[00:09:29.940]what does that mean for the system as a whole
[00:09:34.020]when you warm it up?
[00:09:35.760]And, of course, we could,
[00:09:37.800]it's hard to go out there
[00:09:38.820]and just sort of warm up whole places,
[00:09:41.040]so what we usually do is bring them into the lab
[00:09:43.530]and warm them up in the lab,
[00:09:45.210]and then measure what's going on,
[00:09:46.560]and what are the consequences for communities
[00:09:49.650]or populations when you warm them up?
[00:09:52.260]And how does a change in the predator-prey interaction
[00:09:55.980]cause that?
[00:09:57.180]So, in that sort of predator-prey climate adaptation thing,
[00:10:01.920]anything goes kinda in my lab, usually,
[00:10:04.650]as long as you can find a volunteer, basically, right.
[00:10:08.910]What species we work on,
[00:10:11.490]whether it's a proteus or a spider or a bird
[00:10:13.500]or something like that,
[00:10:14.333]all just kinda depends on the question
[00:10:15.960]and whether or not it's convenient.
[00:10:17.880]And sometimes the things we're trying to do are hard to do,
[00:10:22.740]and so we often gravitate
[00:10:24.810]to the easiest possible taxa to work with.
[00:10:29.160]And so here, my lab, my physical lab here is mostly set up
[00:10:33.000]to work with small aquatic creatures.
[00:10:36.330]That could be little crustaceans,
[00:10:40.200]but also microbes like ciliates, paramecia,
[00:10:45.720]things like that, algae.
[00:10:48.210]So anything that's small,
[00:10:52.440]easily fits in a jar or a Petri dish or a test tube,
[00:10:56.730]but big enough usually that we can with our eyes
[00:11:00.390]see them eating other things.
[00:11:03.330]I do actually like all the predators.
[00:11:05.520]They're all amazing in all the own interesting ways, right,
[00:11:09.270]but I'm probably most fond of hawks and owls, right.
[00:11:15.691]All of my earliest work was with hawks,
[00:11:19.380]Cooper's Hawks, Sharp-Shinned Hawks, but also some eagles.
[00:11:23.880]But then I did a lot of work with owls,
[00:11:26.490]and so they kinda have worked their way
[00:11:29.490]into the sort of mythos of my view of the world.
[00:11:33.210]And we try to work with them a little bit still,
[00:11:37.800]but we have projects out at Crescent Lake
[00:11:41.731]working with Barn Owls,
[00:11:44.880]and they're very difficult to work with,
[00:11:47.040]even though even that site is relatively easy to work at
[00:11:51.990]compared to other places we could work with raptors.
[00:11:56.490]Cedar Point is a field station
[00:12:00.090]run by the Biological Sciences program here at UNL.
[00:12:03.030]It's been just about 50 years.
[00:12:05.610]Next summer, 2024, will be our 50th year,
[00:12:11.280]and people do a lot of different things out there.
[00:12:14.580]We have classes, of course,
[00:12:15.990]in the Artist in Residence program,
[00:12:19.530]but a lot of research of various kinds.
[00:12:21.330]The strong points over the years
[00:12:22.920]have been ornithology and parasitology,
[00:12:25.470]some grassland community ecology work,
[00:12:27.600]and, of course, some predator types of work, limnology.
[00:12:31.380]People don't focus on the lake
[00:12:33.360]quite so much as you might think.
[00:12:35.850]Mostly kind of on the terrestrial side,
[00:12:40.170]but a lot of the marshy and other kind of aquatic habitats
[00:12:42.900]have a ton of things
[00:12:45.270]that harbor all sorts of crazy parasites.
[00:12:47.640]And that has been a huge focus
[00:12:49.560]of Cedar Point over the years.
[00:12:53.280]Field work is, it's great in many ways, right,
[00:12:57.840]'cause it's really grounding.
[00:13:02.133]Biology, there's so much in biology,
[00:13:05.430]it's a gigantic discipline,
[00:13:07.290]and everything is conceptual and abstract, right,
[00:13:10.530]and it really starts to kinda get purchase in your mind,
[00:13:15.510]when you can see things in the real world, right.
[00:13:20.670]Like whether it's actually
[00:13:22.530]just observing a parasite in something
[00:13:24.750]or witnessing a predator-prey event,
[00:13:26.820]or just being outside for a few weeks
[00:13:32.580]collecting data of some sort.
[00:13:34.770]All of the above basically can, I dunno, ground
[00:13:38.790]and make biology seem more real, more tangible.
[00:13:41.850]And I think just connecting to nature
[00:13:46.020]and kind of learning about things in a place
[00:13:49.530]has a pretty positive impact on most people,
[00:13:53.610]and very memorable, and kind of sticks with you, right.
[00:14:00.210]Just learning about something,
[00:14:01.620]when you're out in the middle of it,
[00:14:03.000]it just, I don't know,
[00:14:04.170]tends to burn into your brain better
[00:14:06.240]than when you are sitting in a classroom.
[00:14:09.840]The idea of a course at Cedar Point
[00:14:12.000]is to get everybody out there,
[00:14:13.800]and then everybody's gonna have
[00:14:14.880]their own kind of magical experience, right,
[00:14:18.600]whether it's a research project
[00:14:20.310]or a particular thing they saw or found
[00:14:25.620]or just time on the water in a canoe
[00:14:29.880]or a particular sunrise or whatever it happens to be.
[00:14:34.740]All of those things happen,
[00:14:37.110]and everybody has their own version of that,
[00:14:40.350]but it all has the same kind of effect, right.
[00:14:44.310]And so a Cedar Point class, a good Cedar Point class,
[00:14:47.940]gets a dozen people out enough
[00:14:51.810]that they really have a lotta chances
[00:14:54.120]for many different kinds of interactions
[00:14:57.870]and experiences in nature,
[00:15:00.840]from little adventures to surprise observations.
[00:15:06.120]We'd like to thank Dr. DeLong
[00:15:07.500]for speaking with us today.
[00:15:09.120]Find all of our short Great Plains talks and interviews
[00:15:11.880]as videos and podcasts at go.unl.edu/gpanywhere.

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Great Plains Anywhere: John DeLong on Predators

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