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Thesis defense
- 1. Master’s Thesis Defense Shakira G. Quiñones Lebrón Do calves matter?: The effect of dolphin watching on the acoustic behavior of a population of bottlenose dolphins in Panamá Thesis Committee: Dr. Laura May Collado Dr. Alberto Sabat Dr. Mitch Aide Dr. David Logue
- 2. OVERVIEW • Introduction to whale watching • Chapter 1: Importance of calves when studying impacts of whale watching • Chapter 2: Case study – Acoustic behavior bottlenose dolphins of Bocas del Toro, Panamá • Conclusions • Outreach • Future work
- 3. WHALE AND DOLPHIN- WATCHING History: • From whaling to watching. IWC 1994 • 119 Countries • WW generates $2.1 billion • Recreational use ≠= sustainable use
- 4. THE EFFECTS OF WHALE - WATCHING Short-term Long-term consequences consequences • Boat strikes • Increased death • Disruption of rates important behavior • Abandonment of the • Disruption of acoustic area communication. Bottlenose dolphins - – Doubtful Bottlenose dolphins Shark Bay Population Consequences of 2005) Sound, Acoustic (Bedjer NZ (Lusseau and Bejder 2007) Disturbances (PCAD) model
- 5. POPULATION CONSEQUENCES OF ACOUSTIC DISTURBANCES (PCAD) MODEL What factors influence behavior changes?
- 6. CETACEAN SOUNDS Cetaceans rely almost entirely on sound to communicate. Baleen whales: Low frequency modulated sounds Sperm whales: Clicks (Codas) Other odontocetes: Higher frequency modulated sounds and pulses
- 7. WHALE WATCHING AND NOISE The noise produced by the engines overlaps with the communication signals of many marine mammal species. Masking Erbe 2002 Clark et al. 2009
- 8. RESPONSES TO BOAT APPROACHES Behavior responses Acoustic responses • Behavior state • Rate of communication • Swimming synchrony signals • Inter-breath interval • Acoustic parameters of • Direction and speed of communication signals movement
- 9. FACTORS INFLUENCING RESPONSES TO DISTURBANCE • Experience • Group size • Received levels (RL) • Group composition of noise (mothers and calves). • Distance and speed of watching vessel
- 10. CHAPTER 1: DO CALVES MATTER?:ADDRESSING THE IMPORTANCE OF INCLUDING CALF PRESENCE IN THE ASSESSMENT OF WHALE- WATCHING IMPACTS.
- 11. Introduction • Calves are more susceptible to boat approaches. • Having calves could affect mother’s responses to whale watching. • Is it important to consider responses by groups with calves? • Method: Literature review
- 12. Table 1. Summary of published work on whale and dolphin watching showing the proportion of publications where calves are considered as a factor for changes in responses. Calves responded No difference in Species Calves where not considered differently response Behavioral responses A. bottlenose dolphins (Tursiops Nowacek et al., 2001; ? Acevedo, 1991; Constantine, 2001, truncatus) Hastie, 2003; Lusseau 2004; Buckstaff, 2004*; Lusseau, 2003*; Akiyama et al 2007 2004,2006; Mattson et al. 2005; Arcangeli et al. 2009, Mattson et al. 2005; Janik, 1996) Indo-Pacific bottlenose dolphins Stensland and Berggren ? ? (Tursiops aduncus) 2007; Hawkins and Gartside, 2010 Pantropical spotted dolphins (Stenella Montero-Cordero 2007 ? ? attenuate) Sotalia costero (Sotalia guinensis) Santos et al. 2006 Filla et al. 2009 ? Common dolphin (Delphinus delphis) Stockin et al. 2008 ? ? Killer whale (Orcinus orca) Williams et al. 2002* ? ? Irrawady dolphin (Orcaella brevirostris) ? Hashim & Jaaman 2011 Chinese white dolphins (Sousa chinensis) ? Hashim & Jaaman 2011
- 13. RESULTS - BEHAVIOR STATE Sotalia guianensis Pantropical spotted Bottlense dolphins Santos et al. 2006 dolphins Stensland & Berggren Montero-Cordero 2007 2007 Lemon et al. 2006 Less resting and feeding during interactions with Arcangeli and Crosti boats for groups with calves. More traveling. Lusseau 2003 Lemon et al. only found changes from traveling to milling Lusseau found changes in female avoidance strategies
- 14. RESULTS - DIRECTION AND SPEED OF MOVEMENT Bottlenose dolphins - Steckenreuter et al. Humpback whales- Stamation et al. 2011 2009, Schaffar et al. 2008 Killer whales - Williams et al. 2002 Gray whales??
- 15. RESULTS - INTER-BREATH INTERVALS Bottlenose dolphins - Nowacek et al. Humpback whales - Stamation et 2001, Lusseau 2003 al. 2009 Groups with calves spend more time underwater: Vertical avoidance Sotalia guianensis - Filla & Monteiro 2009
- 16. RESULTS - SWIMMING SYNCHRONY Not enough evidence. Groups with calves are generally less synchronized. Synchronization increases with the presence of boats.
- 17. RESULTS - ACOUSTIC RESPONSES Production of communication signals Groups with calves have a higher whistle production rate. For humpback dolphins, whistle rate increases when disturbed by boats, particularly when calves are present in the group. Lemon et al. 2006 found no reponse. Did not considered calves.
- 18. CONCLUSIONS Do calves matter? • Yes. Average of response vs. targeting vulnerable groups. • Better prediction of long-term consequences.
- 19. CHAPTER 2: DOLPHIN-WATCHING BOAT INFLUENCE DOLPHIN COMMUNICATION: THE EFFECT OF NUMBER OF BOATS AND MODE OF APPROACH ON WHISTLE EMISSION RATE FOR GROUPS WITH CALVES
- 20. INTRODUCTION DOLPHIN COMMUNICATION SIGNALS Whistles are frequency modulated signals used for communication. 20Hz – 32kHz Each individual has its own “signature whistle” used for group cohesion. Whistle rate overall vocal behavior but can be used as a measure to noise impacts. Whistle rate = #whistles/#dolphins/time
- 21. Dolphins can potentially increase their whistle repetition to compensate for the masking noise. Separation between mothers and calves elicit a higher whistle rate. Buckstaff 2004
- 22. DOLPHIN WATCHING IN BOCAS DEL TORO Small resident population of bottlenose dolphins (~100 dolphins) Daily interactions with dolphin-watching tour boat. Feeding Social
- 23. PREVIOUS STUDIES IN BOCAS Change in frequency and duration of whistles. (May Collado & Wartzok 2008) Increase in call repetition. (Taubitz 2007) Ambient noise in Bocas del Toro May Collado & Wartzok 2008 Changes in behavior (Barragán-Barrera 2007) Calves?
- 24. Questions: Does dolphin-watching have an effect on whistle rate? Is it different for group with calves?
- 25. Challenges: Noise received levels (dB)? Too many boats at the same time Few dolphins Solution: Use type of approach and number of boats as a relative measure of acoustic disturbance. Signal:Noise (dB) Distance from observation boat Buckstaff 2004
- 26. MEASURING DISTURBANCE # Boats Type of Description approach Aggressive. Boats approaching dolphins at high N speeds, perpendicular to the O # 1 dolphins’ swimming B direction, and/or circling the I O A group. Closer than 10m. S T Close approaches (<10m), 2 changes in speeds towards E S the group. Low speed. Non aggressive. Parallel approach at distances greater 3 than 20m. Slow speed or engine off.
- 27. FIELD METHODS 2012 Acoustic & Behavior recorder Behavioral Acoustic recordings (1 state min)
- 28. FIELD METHODS 2012 A RESON hydrophone was deployed at 2 m depth when the engine was off to record and listen the dolphins’ whistles. Sampling rate: 75kHz Broadband
- 29. FIELD METHODS 2012 Photo ID Acoustic & recorder Behavior recorder Boat Behavior Grumpy recorder captain Subject swimming away Behavioral state Acoustic recordings (1 min) Pod size # boats present Presence of calves Type of boat approach
- 30. RESULT S Do calves matter? Presence vs. absence of boats (Whitney U-test X2 = 2210, p-value = 0.070) Presence vs. absence of boats with and without calves (Friedman’s X2 = 73.91, df= 3, p-value = 0.000)
- 31. Mother-calf spatial relationship could be important Supermessy and baby:
- 32. RESULTS Number of boats No clear pattern of response to number of boats. Groups with calves always had a higher whistle emission rate. Num. of boats
- 33. RESULT S Type of approach Aggressive approaches showed higher whistle emission rates for both groups with and without calves. AGGRESSIVENES
- 34. RESULT S Behavior state Behaviors that require group coordination show a higher whistle emission rate
- 35. CONCLUSIONS Do calves matter? Yes. • Groups with calves show a different response to the presence of boats. • Aggressive approaches elicit a higher whistle rate for both groups with and without calves. Can be a better measurement for relative noise disturbance. • Behaviors that require cohesion showed a significant acoustic response to presence of boats. • Enforcement of the regulations is required to avoid negative long-term consequences.
- 36. OUTREACH Webpage Facebook page Local TV interview STRI news
- 38. FUTURE WORK Recommendations for Future work: management: • Continue with • Slower speeds outreach work • Less boats at a time • Photo Identification of • Avoid groups with the population. calves. • Estimating population • Self-regulated size. industry by the • Playback experiments formation of alliances. (collaboration with Susan Parks – Syracuse University)
- 39. ACKNOWLEDGEMENTS Thesis Funding and support: Committee: Dr. Laura May Collado Dr. Mitch Aide Dr. Alberto Sabat Dr. David Logue
- 40. ACKNOWLEDGEMENTS Field assistants Presentation & Manuscript Friends & Family: THANK YOU! – GRACIAS! “I have always depended on the kindness of strangers” – Blanche Dubois
- 41. Q Questions?
Hinweis der Redaktion
- First I will give you an introduction to whale watching and its history. Then I’ll go into my first chapter, which is a literature review about the importance of including calves when studying behavioral responses to whale watching.Then I’ll go into the details of my study case in Bocas del Toro, Panamá where I studied the effects of dolphin watching on the acoustic behavior of bottlenose dolphins.And finally, I’ll wrap it up with some general conclusions, the outreach project we’re doing in Bocas and the future work.
- So, recreational observation of marine mammals (whales and dolphins) started many decades ago, but it grew stronger in 1994 after the International Whaling Commission suggested the need of a more sustainable use of whales and dolphins. Back then, populations were declining due to a very large harvesting rate. Therefore many countries switched from whaling to watching. This also helped many small local communities around the world that depended on unsustainable fisheries.By 2008 there were 119 countries that were whale watching generating $2.1 billion annually. However, whale watching around 70% boat based, which represents a human disturbance that can be aggravated with the increase of boats. Therefore, whale watching is not necessarily sustainable.
- For example, whale watching can have negative consequences. An increase in number of boats in their habitat of marine mammals also increases the changes of collisions with boats. In addition, interactions with boats can disrupt important behaviors. For example, if a pod of whales is feeding, they may stop feeding to swim away from the boats. And also, because of the noise created by the boats, their communication can be disrupted. These short term consequences Estosefectosnegativos a cortoplazo son el incremento de la probabilidad de colisiones con embarcaciones, la interrupciĂłn de comportamientosimportantes (comoporejemplo, un grupo de ballenaspodrĂadejar de alimentarseparahuir de un bote), y tambiĂ©n el ruidogeneradopor los motores de los botespodrĂainterrumpir la comunicaciĂłn entre lasballenas.Todosestosefectos a cortoplazo, con excepciĂłn de lascolisiones, no tienen un efectonegativoque sea evidente a nivel del organismo o de la poblaciĂłn.Sin embargo, a largo plazo se ha observado un aumento en lastasas de mortantad en poblacionesexpuestas a mucho tráfico de botes y tambiĂ©nabandono de hábitatsimportantes.
- To connect the short term responses to long-term consequences, a conceptual model was developed. It’s called the population consequences of acoustic disturbances, but can be applied to any other disturbance, not just noise. So, the behavior changes can have affect a life function, than affects a vital rate such as survival or reproduction which at the ends can affect the population.When we are studying the changes in behavior, there are several factors we need to consider.
- First, we can look at how the noise created by the boats may affect communication. In a marine environment, where light is limited, sight is not a reliable sense, so marine mammals developed ways to interact with their surroundings and their mates using sound. Most marine mammals use sound to communicate with one another. And these sounds are mostly constrained by the size. For example, baleen whales produce low frequency tonal sounds. While toothed whales produce frequency modulated sounds that are higher in the frequency spectrum like this of the common dolphin. This graph here represents an audiogram of 6 different species and populations. An audiogram is a representation of the how loud a signal has to be in a certain frequency so that the species can hear it. The line represent the threshold in which noise causes temporary hearing loss. Than can be extrapolated to the actual noise levels.
- Here is an example of engine noise extrapolated to an audiogram of killer whales. In the frequencies between 2 and 60 kHz, the noise is over the hearing capabilities of whales.Those are the same frequencies in which they produce their communication signals meaning that the noise can interfere with their communication.Here is a graphical example. These are fin whale calls. In habitat A there is very little background noise while in habitat B is very noisy. So, when dolphin watching boats are approaching whales or dolphins, they can hear the boats at least a few hundred meters before they come close enough for whale watching. How do they react?
- Reactions to boats can be divided into behavior responses such as behavior state, swimming synchrony, time spent underwater, and direction and speed of movement.And because communication might be hindered by the noise, they show acoustic responses. For example, they can increase the rate of communication signals or adjust the acoustic parameters to make sure they convey their message. So, what are the factors that influence these responses?
- Factors include the level of experience with boat trafficThe received noise levelDistance and speed of the watching boatGroups sizeAnd group composition, for example, having babies in a group. And that last one is the focus of my first chapter
- Basically, my first chapter addresses the importance of including calves when studying behavioral responses to whale watching.
- This is half of the table for my review. I found all the possible studies of whale watching I could in period of time and looked at behavioral and acoustic responses to boats when they consider calves and when they don’t.The following will be examples of what I found34 case studies
- So, for behavior state, the tendency is that overall, there is less resting and feeding and more traveling. This was true for all these species. For sotalia dolphins, for example, they found that groups with calves engaged in more traveling behavior than groups without calves. Same with pantropical spotted dolphins.In the case of bottlenose dolphins, one of the studies that did not consider calves and they did not find any responses to dolphin watching boats. In another case study, Lusseau did not consider calves but instead he measured differences in avoidance strategies between males and females and he found that females change to diving behavior more often than males.
- Another avoidance strategy is to swim faster and change the direction of the movement to avoid vessels. Killer whales, female killer whale for examples show more erratic movements than males in the presence of boats. If they have calves, they’re probably more susceptible to interactions with boats and avoid them more often. In addition all the moving around limits the time they have to nurse, which can have a long-term impact on this population. Humbpack whales for example, also change direction but mostly when they did not have calves. Groups with calves engaged in more diving instead. In addition, when they have calves, they swim slower. For bottlenose dolphins, having groups with calves also increases the erratic movements.But in the case of gray whales, they only studied the southbound migration, but when they travel back to the north they might be accompanied by calves, so this needs to be studied in the future.
- Interbreath intervals refer to the time between breaths, and also the time spent underwater. Mothers with calves tend to prefer this type of avoidance to boats. And this is true for at least the three species depicted here.
- When it comes to swimming synchrony, there is not a lot of evidence to compare groups with/without calves, but generally, at least for bottlenose dolphins, groups with calves tend to be less synchronized. So differences in responses between groups with and without calves is expected.
- So, in conclusion. Yes, they do matter. Do calves matter?Yes. Not taking calves into account could lead to concluding there is no response to a disturbance because researchers are looking at the average response of a group. Future studies should consider calves by doing focal sampling of mother-calf pairs or focal group sampling of groups with and without calves. That way it would be more accurate to predict long-term disturbances at the population levels.
- For my 2nd chapter I studied the acoustic responses to dolphin watching in a population of bottlenose dolphins in bocas del toro that is subject to a growing dolphin watching industry.
- First lets look at dolphin communication signals. Bottlenose dolphins emit frequency modulated signals that range between 20 Hz and 32 KHz. This means they’re very variable and show plasticity. Each dolphin has it’s own signature whistle among their whistle repertoire which is believed to be used for group cohesion. To study disturbance in communication we can look at whistle rate, which is the # of whistles emitted per individual in a period of time.
- To compensate for disturbance, dolphins can change the shape of their whistles or increase the repetition. For example, a study conducted in Sarasota Bay showed that dolphins increase their whistle rate in the onset of boat approaches.In addition, a capture-release experiments showed that when mothers and calves are separated, they increase the repetitions of their call, and so the whistle rate increases.
- Lets go to my study case. In Bocas del Toro, Panamá there is a small resident population of bottlenose dolphins. Population size was estimated to be a bit over a hundred individuals, but there are a lot less of the residents. The residents are very predictable because they live in this very small bay here known as the dolphin bay. Most of the individuals living here are probably females because males tend to have a wider range. However, they do use other areas of the Archipelago. Because of their predictability, a dolphin watching industry has been growing around them. Interactions occur everyday from 9am to noon approximately.
- Previous studies have found that dolphins change the duration and fundamental frequency of their whistle to respond to the noise. This is a spectrum of the noise in different areas of the archipelago. In addition, It was found that they change their behavior state in presence of boats. They engage in more traveling and feed less often. And also, they increase their whistle rate in presence of boats. But what about calves?
- So my two main questions would be if dolphin watching has an effect on whistle rate and if it is different for groups with calves.
- One of the challenges is the fact that I could not measure noise because there were too many boats at the same time at different speeds. So what I did was to use the mode of approach as relative measure of acoustic disturbance. This means that if a boat is closer to the dolphins, the noise received by the dolphins is louder. And if the boat is going at fast speeds, it is also louder.
- So I divided mode of approach into 3 different categories according to aggressiveness being #1 the most aggressive approach: fast speeds, close to the groups and sometimes even circling the dolphins to create a wave. In addition, I used number of boats. The more boats, the louder the noise.
- How does this translate into the field? What I did is that I recorded dolphins continuously in 1 min files. At the same time I noted the behavioral state of the dolphins during that minute of recording.
- I recorded dolphins using a RESON hydrophone connected to an amplifier that send the signal to the computer while I was listening to it at the same time.
- There was an observer taking data of boat presence and behavior, and another observer taking photo-ID of the dolphins and estimating pod size and the presence of calves.Of course, we had our impatient and grumpy captain.
- When I compared whistle rate in situations of only presence and absence of boats there was no statistical differences. But when I added groups with calves as a factor, calves seem to decrease their whistle rate.This reduction could be associated with the spatial relationship between the mother and the calf. If they are swimming tightly together in presence of boats, then increasing their contact calls is not necessary. In addition, it would mean a higher energetic cost.
- There was one particular situation in the field where there were more than 10 boats surrounding the dolphins and us, the research boat. And at one point I started to hear whistles that were very close to the hydrophone. When I looked, there was this known female, Supermessy swimming on one side of the boat and a baby on the other side of the boat. They kept whistling until they met each other right in front of our boat which was a pretty nice evidence of the contact call hypothesis.
- When I looked at number of boats instead, there was no clear pattern of increasing or decreasing whistle rate according to num. of boats. Both groups w/wo calves showed the same pattern which a higher whistle rate for the category of 7-9 boats. And groups with calves always had a higher whistle rate which is consistent with the literature. We did not know which boats had their engines off, because some dolphin watchers do follow the recommendations for sustainable dolphin watching and that can possibly explain the variability observed among the categories of boat numbers.
- In the case of type of approach, the most aggressive approaches had the higher whistle emission rate for both groups with calves in white there and without calves in gray. I did not have any observations of aggressive approaches type 1 for groups without calves. It seems that type of approach was the best way to estimate disturbance since the tendency is much clearer compared to just presence of boats and number of boats.
- Now, when we look at behavior, we see that those that require group coordination showed a higher whistle rate in the presence of boats compared to the absence possibly because they’re more interested in maintaining contact and they increase their call rate to overcome the masking of the noise. Again, we have high variability.
- So, in conclusion. Yes, it is important to consider calf responses when studying the effect of whale and dolphin watching. Groups with calves showed a different response to boat presence. Aggressive approaches elicit a higher whistle emission rate, possibly due to arousal, stress, or to compensate for masking of communication signals.And lastly, dolphins engaged in behaviors that require group cohesion might be more sensitive to acoustic disturbance.Therefore, we suggest enforcement of regulations of dolphins watching to avoid negative long-term consequences in Bocas.These enforcement of regulations can not be possible without educating the people involved with dolphin watching. Therefore, together with my advisor and some colleagues we did some outreach in Bocas.
- I created a webpage about all the dolphin related projects taking place in Bocas. I also created a facebook page. When we were visiting Bocas over the summer, we were interviewed by the local tv channel and the smithsonian published a press release about our work.
- In addition, we did a few talks with different communities of the archipelago and of the schools.
- We gave the people some recommendations for management which include:Slower speedsLess boats at a timeAvoid groups with calves.Self-regulated industry by the formation of alliances.In the near future I would like to continues with the outreach work. In addition we are going to finish the catalogue of the dolphins and estimate the population size.And finally, next summer we are going to measure the noise more accurately and perform playback experiments so we can have more control of the noise exposure and get a more accurate response to the noise.