December 14, 2020 – Dr. Kelly Diehl talks with Dr. Robin Tinghitella, an associate professor of Biology in the Department of Biological Sciences at the University of Denver. They discuss Dr. Tinghitella’s new project to investigate if noise pollution is harming cricket populations and, subsequently, the wildlife food chains of which they are an essential part. In this study, crickets will serve as a model for invertebrates to help answer questions about the health and reproductive consequences of noise.
00:08 Dr. Kelly Diehl: Welcome to Fresh Scoop Episode 27, how crickets can tell us more about urban noise pollution. I'm your host, Dr. Kelly Diehl, Morris Animal Foundation, Senior Director of Science and Communication. And today we'll be talking with Dr. Robin Tinghitella. Dr. Tinghitella is an associate professor of Biology in the Department of Biological Sciences at the University of Denver, and she's a Morris Animal Foundation funded researcher. Fresh Scoop is the monthly podcast of Morris Animal Foundation, one of the largest non-profit foundations in the world, dedicated to funding studies to find solutions to serious health threats to animals. And in each episode, we'll feature one of the researchers we fund or one of our staff members discussing their work in advancing animal health, whether you're a practicing veterinarian, technician or student, or just an animal loving science geek. Fresh Scoop is the podcast for you. You can learn more about us at MorrisAnimalFoundation.org. Okay, on to today's show. Today we welcome Dr. Robin Tinghitella. Dr. Tinghitella completed her PhD at the University of California, Riverside, held post-doctoral positions at Michigan State University and the University of Michigan and has been a faculty member at the University of Denver since 2013.
01:31 DD: Dr. Tinghitella's research interests include a wide variety of things, ranging from animal reproduction to rabbit evolution, to Equity and Science and Science Education. Her lab at the University of Denver focuses primarily on understanding the evolution and ecology of animal behavior, including a recent focus on how environmental change caused by human activity impacts animals. Robin, thanks for joining us today.
02:01 Dr. Robin Tinghitella: Absolutely, thanks so much for having me.
02:04 DD: Before we get into your work, we always ask everyone to tell us a little bit about yourself and your background and kind of how that influenced you to get into the work you do.
02:14 DT: Sure, well, definitely, as you said in your introduction, I'm a faculty member of the University of Denver, but outside of work, I'm also a mom of three, a yoga enthusiast and a big fan of travel, and my work takes me to all kinds of really cool places, most often to Pacific Islands where the crickets that I study live. So my scientific training is really in Behavioral Ecology, which means that I study the fitness consequences of animal behavior, how behavior and changes in behavior impact survival and reproduction, and most of my career has really focused on animal communication and particularly communication that happens between males and females that are making mating decisions. So we've asked questions, for instance, about what are the pressures that really shape the signals that males are using to attract females, and on the flip side, we've worked a lot on understanding why and how females choose the mates that they do, and specifically how the environment and their individual experiences shape the animal decisions. So recently, some of my work has taken a more applied direction to investigate how human-induced environmental change alters animal behavior, and that's really how I got interested in noise pollution and in the work that we're doing with support from the Morris Animal Foundation.
03:33 DD: Can you tell us a little bit about some statistics surrounding noise pollution, I think everybody gets the idea like stuff is just noisier, but can you give us a bigger picture on that particular problem?
03:48 DT: Sure, human-generated noise, is clearly as you said, a major and expanding global pollutant, we've all experienced it, whether that's hearing road traffic or air traffic or fireworks or listening to a concert of in the distance or just the background hum of your loud refrigerator, and as researchers, we tend to think of noise as unwanted or inappropriate sound that interferes with normal activities, things like sleeping and conversation. In other words, it's noticeable, it attracts the attention of an organism whose focus was on something else before, and if we use that definition, it turns out that more than 83% of land in the Continental US, for instance, is close enough to a road to be exposed to noticeable vehicular noise, and that's a problem that's getting much worse. Since 1970, road traffic has actually tripled in the United States, and it's not just road traffic that generates noise, it's air traffic and boats and concerts and energy extraction, and we know that in humans noise impacts help by contributing to things like hearing loss, elevated stress hormone levels, hypertension and disruptions to sleep, but those negative consequences of noise aren't limited to humans. Noise knows no bounds.
05:05 DT: It travels really well. So those animals that are living with us in human adjacent communities, and even in places like national parks that we might expect to really be protected from these sorts of problems are also impacted, so there's really a growing body of literature showing us that noise reduces animal's ability to hear natural sounds, it induces stress responses, it interrupts a huge variety of behaviors from foraging to vigilance and parental care, and it even increases mortality and reduces reproductive success.
05:37 DD: Wow, I think people understand dog whistles, you know what I mean? That there are the frequency... Do other animals have... Are they more sensitive because their range of available sounds is greater than ours?
05:53 DT: That's a great question. So the sort of sensory systems of animals are a really important part of this type of study, people will often ask questions about whether the same noises that impact us are the ones that are impacting different groups of animals, and you're absolutely right that that's completely dependent on the sensory system of those organisms, what are the frequencies that they are capable of hearing? So for the invertebrates that we work with, and a lot of organisms like birds that people are familiar with, and think of in the context of noise. Yeah, they really are capable of hearing sounds that are in the frequency range that human-induced noise is at. So those sounds that we're producing overlap with the hearing ability in those animals and the important sounds that they're producing to communicate with one another and to do things like detect predators.
06:48 DD: Wow, so let's dive into... That's a good lead into your Foundation-funded study, can you start by giving everyone sort of a high-level view of what you are proposing to do?
06:58 DT: Absolutely, this study is really designed to, as comprehensively as we can, assess the impacts of human-generated noise on the health and welfare of invertebrates in particular, and we'll be doing that across multiple generations, so essentially what we'll do is expose crickets to traffic noise that we already know from previous work overlaps with their range of hearing and interrupts their communication, and in the context of this big experiment, we'll learn something about the mechanisms that might be responsible for reduced survival and reproduction of field crickets that are reared in noisy environments. We'll also be able to hopefully identify the levels of noise that induce biologically important responses, and we'll look at whether removing sources of noise can actually mitigate some of the problems that are induced by very early developmental exposure to noise.
07:54 DD: I'm going to lump two questions together: First, why invertebrates, are you alluded to it, and then can you say how invertebrates, like how important they are in our environment and food webs?
08:09 DT: Sure, so there were really three things that kind of motivated me to start working on the effects of human-generated noise on invertebrates. First off, they comprised most of the biodiversity on Earth, and they're really important players in a number of food webs, so we know that their loss could have very important cascading negative consequences for the ecosystems that depend on them, so as I mentioned earlier, these important roles in ecosystems are things that we want to think about, and food webs are really just a visual representation of all of the sort of interconnected linear food chains within an ecosystem. In other words, they’re a picture of what organisms eat which other organisms and how the energy and nutrients flow from one organism to another. In terrestrial food chains, we often find that invertebrates are one of the lower trophic levels. In other words, they're eaten by lots and lots of other animals that we might be more familiar with, and those animals are in turn by... are eaten by others on and on. So one of the reasons that we should be really concerned about the effects of environmental change on invertebrates is that negative impacts on invertebrates have cascading effects on other organisms that they interact with, including through these food webs.
09:27 DT: A second reason that I wanted to work on invertebrates in this study is that one of my major study systems in my lab is the Pacific field cricket, and like lots of animals, hearing and the sound scape around them is really important for these guys, they use song to find each other, to fight with each other, to decide who to mate with, and they use sound as a primary mechanism of detecting things like predators that will eat them. They also live alongside humans, and like most invertebrates, they're capable of hearing sounds in the frequency range of human-produced sound, and they rely on communication in that range. So noise that we're producing has the potential to directly interfere with invertebrates' survival and reproduction, if it masks their ability to hear natural sounds, causes them to leave, distracts them from important tasks, stresses them out or leaves them immunocompromised. And then finally, when I started down this road a number of years ago, as I started reading to learn more about what we already knew about the effects of noise on animals, I discovered that most of the work on noise in terrestrial environments has come from some really cool field studies on vertebrate animals.
10:41 DT: There was a review paper a few years ago, for instance, in which the authors found that only 4% of work on noise has addressed effects on invertebrates, and that work in vertebrates is really amazing and has taught us a lot but one major advantage of instead using an invertebrate is that we can actually test ideas that require experimental designs and sample sizes that are unreasonable or even logistically impossible for a vertebrate study system. But we hope that these things that we do will really reveal principles that are transferable to other organisms. So in this case, crickets offer us this cool opportunity to isolate the impacts of noise from other stressors that animals experience in the wild, and to conduct very manipulative experiments in which we follow our exposed animals and their offspring throughout their entire natural lives to assess the longer term consequences, then we might be able to infield studies of a much longer lived vertebrate.
11:40 DD: So I was sharing with Robin in our communication before this that this represents a really unique study for the Foundation, we have done some invertebrate work, we've done oysters, just to give an example, but they're really neglected, and I think Robin pointed out to me very eloquently in her grant proposal, here on the podcast, how important and overlooked, I mean they're not just gross bugs, I think people might think they’re gross bugs, but how important they are to all of us and are sadly neglected as far as what we can do, not just to help them, but as a really cool model system. One of the objectives, when I was reading your grant that I didn't quite understand, I'm going to ask you to explain, is what you call the trans-generational parental effects of noise. And so can you dive into that for us?
12:38 DT: Sure, so in this project, instead of just looking at the effects of noise on a single generation of crickets, we're actually going to rear crickets under different noise conditions, and then allow them to mate in the lab and look at what happens to their offspring, even when those offspring are not exposed directly to noise themselves. So why are we doing that? Well, we're doing that because we're really interested in something called parental effects, that is any sort of lingering impacts of parents' exposure to noise on the offspring, and parental effects are just ways aside from shared genes that parents experience can actually change the traits of their offspring. So sometimes that happens through changes in gene expression, turning on or turning off particular genes, or through changes in parental care, for instance.
13:32 DT: You might have heard of these types of effects referred to as either inter or trans-generational effects, and we know that there are parental effects on all kinds of things like learning, anxiety and stress, anti-predator responses, dispersal, development time, and pretty much every single morphological characteristic you can imagine. And there's been a lot of interest in these trans-generational parental effects recently, because in some cases, they're actually preparing offspring for the environment that their parents experienced, in other words, we would call them adaptive, we know that there is some indication in the literature now that noise pollution might also have effects on animals that last beyond a single generation. So in this big experiment that we're doing, we'll have the opportunity to test that hypothesis.
14:20 DD: Okay, and could you talk a little bit about some of the methods that you're using and then... I have a question. An extra question for you. So start with the methods.
14:35 DT: Okay, so in this project, we are building on an existing sort of experimental design that we've been using in my lab recently to really isolate, like I said before, the effects of human-induced noise specifically on the animals. So what we do is rear a first generation of crickets from egg to maturity in the lab, and we do that under one of four different noise conditions, in this case, we're exposing them to anthropogenic sounds, traffic noise that we recorded right here in Denver, and we'll play that back to the animals at one of three different realistic volumes that they might experience in their lives, or under a silent control. So in our lab, we very lovingly call these Frankenbator experiments, because what we do is rig up a bunch of different incubators in the lab with a huge number of Bluetooth speakers inside of them that we use to broadcast the sound treatments inside of the incubators that we raise the animals in.
15:34 DT: So then when those animals become adults, we actually switch the treatment that they're in and rear them in a new randomly determined noise treatment, one of those four that I mentioned earlier, and we do that until their natural deaths, and doing that actually allows us to look at the effects of exposure to traffic noise during development, that egg to maturity stage, separate from any effects of traffic noise that are experienced during adulthood, and we think that's a really important part of this design because it mimics real life. Animals often leave poor or stressful environments when they reach adulthood and are capable of dispersing, and we've used this design in the past and found some really interesting but unfortunately compounding negative effects of noise on behavior and life history and reproduction. For instance, we know that exposure to traffic noise slows down cricket development, that reduces the length of their adult lives and it impedes the ability of female crickets to find mates using their songs.
16:37 DT: So in this experiment, we're really interested in looking at some possible mechanisms for those patterns, so when the animals reach adulthood we'll be measuring things like their ability to mount an immune response, because we know that there are connections between stress that's experienced early in life and immune compromise of adults. So one of the things that you do is just a hemocyte count, those are just the specialized immune cells that help animals to encapsulate foreign bodies that get into them. So what we actually do is simulate a getting attacked by a parasitoid, so we inject a little tiny piece of nylon filament into the animal, and in order to sort of mount an immune response against something like a parasitoid egg or larvae, the crickets actually encapsulate them with layers of hemocytes to keep the invader from being able to breed, so they asphyxiate it, and in the process, those cells die and they melanize or darken, so we actually measure how dark that little filament gets as a proxy for their ability to mount an immune response.
17:45 DT: And then in terms of fertility, we are measuring the weight of reproductive organs for males and for females, and then we're measuring the quality of the male ejaculate, you just take this little... they produce these sperm-containing packets called spermatophores, and you just take one of those sperm-containing packets and use this live sperm/dead sperm assay that allows you to stain live sperm one color and dead sperm another, and the ratio of live to dead sperm is a really important and flexible component of the sort of reproductive system of male crickets.
18:21 DD: Wow, that's pretty cool. And just for everyone who's listening, as Robin mentioned, this is normal noise, not like the front row on Metallica concert, and for you young people, you can go look up that band, but I got the idea is this is what they would normally hear, and you talked about this, though you didn't use this word. Is this like stress? Stress on these guys?
18:48 DT: It could be, yeah, absolutely. One of the things that I think has come out of a lot of the noise research recently is that there are bigger impacts of noise often on survival and reproduction when it is not predictable, so when you don't expect that loud noise to happen or that truck to zoom by that actually disturbs animals more than a sort of traditional background sound, a hum of the city. So we think that, yeah, it does seem to be stress that is disrupting a lot of these experiences and functions that animals normally have.
19:25 DD: Which actually makes me think of another question. So I'm putting Robin on the spot here a little bit. Yeah, we talk a lot about... People are familiar with white noise, right? As for folks sleeping, for those of us who have kids and we're playing quiet music in the background, do crickets be okay with certain amounts of white noise or not really, because they're so sound, they need their songs and other things to survive?
19:56 DT: That's a great question. I'm not sure that we know the answer. I can tell you two things. One is that in the earliest iterations of designing this kind of Frankenbator noise experience for the crickets, we started doing things like measuring how loud our incubators actually were in the lab, and they produce white noise, they have that sort of hum of a refrigerator or an incubator in the background, and we discovered that when we were playing back these traffic noises, they were actually being drowned out by the sound of our incubators themselves, so we turn our incubators completely off when we do these experiments in order to broadcast these sounds. But it made us really concerned about things like whether our normal rearing environments that we keep these animals in in the lab might actually be inducing some of the same effects that something like a disturbing traffic noise in the field would.
20:53 DT: The other thing that I'll say is from a completely separate experiment, one of the animal communication studies that my lab is working on has us doing what we call cricket races, where we ask crickets to tell us which sounds they like, and we use white noise as our negative control, so we don't think that crickets are attracted to white noise, and that's what we find in these studies, we'll play different sounds or the different cricket songs for them, plus white noise, and they don't go to the white noise, so it's not attractive to them in the sense that some ecological traps are like lights for baby turtles that are hatching, things like that, so it doesn't have that sort of an impact, we've never seen any direct impacts, obvious changes in behavior when we're exposing them to that type of a sound, but I don't know that anybody has actually looked at this sort of thing at all. And any organism that I'm aware of actually.
21:54 DD: I'm glad you talked about that, because I was wondering like how do you just muffle everything else? Because as you said, you think about vibrations and again, sound's weakened here, so that's really interesting. You talked about this as well, because I know you've looked at other animals, we're talking about people, do you think your findings from this study might have broader applications to birds, mammals, even people?
22:24 DT: Great question. I think that's tough. It's hard to say. So some of the characteristics that we're looking at, we really chose specifically because existing studies in vertebrate animals suggest that they are affected by noise, for instance, a lot of noise work has been done in wild bird populations, we know that some birds experience reduced fertility in noisier locations, and there's some limited evidence in mice, for instance, that parental effects of noise do things like reduce secondary immune responses of offspring, but I think whether our results will really sort of parallel those effects that noise has on other animals depends on a lot of things. One of those that we already talked a little bit about, which is the sensory abilities of the animals, what they can hear, the extent to which noise masks their ability to hear sounds that are important to their survival or reproduction, and even on things like the particular noise stressors that they're exposed to, and the ways that those stressors manifest in different species.
23:24 DT: So certainly I think that our work will provide us with a suite of characteristics to look at more seriously in other organisms where that's logistically possible. And again, more broadly, once we know how noise effects in vertebrates, I think we can also begin to think about and really examine the effects of noise on entire communities of organisms in the wild. If exposure to traffic shortens adult lifespans and reduces the ability of insects to find mates and reproduce, for instance, does that reduce population sizes and how do smaller insect population sizes affect the animals that eat them and the animals that eat those animals, and so on?
24:06 DD: I know I'm going to ask you to speculate on this and you're just starting your research now on this particular project, but do you have a sense depending on what you find now, where you're going to go next? Like what you would like to look at next.
24:21 DT: I think we're very interested in taking this out to the field, so over a couple of summers with some really great undergraduate researchers, we've been establishing some local field sites in and around Denver that occur along sort of a noise gradient, so from urban to rural environments, and we're interested in looking at things like whether there are new differences in the timing of doing certain behaviors or the frequency of doing certain behaviors, or the abundance of particular insects that are living in those communities along that sort of urban to rural gradient. So we're really interested in using our opportunity to manipulate the noise environment in the lab to figure out which things we should be measuring in these field populations that we can work with in a while.
25:10 DD: Awesome. To wrap up, what do you think your take home message is for our listeners, and we have veterinarians, like I mentioned, we have vet techs, we have vet students, we have owners, when it comes to dealing with noise pollution in general, and maybe even what we should be aware of as we live our lives, because I know we're the main culprits for perpetuating this stuff.
25:37 DT: Right, I'd really, I think love for all of us to just start to notice unwanted sounds, we often don't think about them, we sort of get used to them and they fall off into the background, and just to think a little bit more about how we're changing the world around us and what that means for the animals that we live with, so turn things off when you can, think about whether your recreational activities impact animals negatively, and maybe protect your pets from the stressors of human noise as much as possible. And beyond that, I hope this work really addresses an environmental issue that causes morbidity and mortality in a wide variety of wildlife, but maybe addresses that issue from the perspective of a key group of animals that have been overlooked and whose livelihood can have huge impacts on other animals and their ecosystems more broadly.
26:28 DD: Robin, thanks so much for joining us today and telling us about this issue, and we'll look forward to reading about more of your work on this topic, and we're so excited at the foundation to be able to fund this.
26:39 DT: We are too. Thanks again for having me. It's been really fun.
26:43 DD: So that does it for this episode of Fresh Scoop, and once again, thanks to Dr. Robin Tinghitella for joining us. We'll be back with another episode next month that we hope you'll find just as informative. The science of animal health as we know is ever-changing, and veterinarians need cutting edge research information to give their patients the best possible care, and that's why we're here. You can find us on iTunes, Spotify, Google Play Music, and Stitcher. And if you liked today's episode, we sure appreciate if you would take a moment to rate us since that will help others find our podcast. And of course, to learn more about Morris Animal Foundation work tins work as a whole, go to MorrisAnimalFoundation.org, there you'll see just how we bridge science and resources to advance the health of animals. You can also follow us on Facebook, Twitter and Instagram. I'm Dr. Kelly Diehl and we'll talk soon.