Doctoral Programme on Marine Ecosystem Health and Conservation
 PhD Subject Catalogue Fourth Edition - 2013
Driven to distraction: Behavioural consequences of noise pollution across multiple contexts in the European hermit crab
PhD Code: MARES_13_05:
  • Host institute 1: P7 - University of Plymouth
  • Host institute 2: P4 - Galway Mayo Institute of Technology (GMIT)
Research fields:
  • T5 - Ocean noise pollution
  • Briffa Mark -
  • Gammell Martin -
Contact Person and email: Briffa Mark -

Subject description
Important Note : This PhD Subject can only accept Euroepan Category B candidates. 

Ocean noise pollution has the potential to disrupt critical behaviours in a vast array of marine an species that are well known for relying on acoustic information. There are two mechanisms through which ocean noise may impair animal behaviour. First, noise may mask auditory information. Second, noise is also known to distract attention from other sources of information (Dukas 2004). Chan et al. (2010a, b) proposed a ‘distracted prey hypothesis’ to explain the finding that terrestrial hermit crabs responded to a visual predator cue more slowly in the presence of boat noise. This demonstrates the potential for noise pollution to effect behaviours that are stimulated by non-auditory information. Marine hermit crabs are globally distributed and represent a significant component of the inter-tidal, coastal shelf and deep-sea fauna across the world (Briffa & Mowles 2008). Our work on aggression (Briffa et al 1998, 2000, 2001, 2002, 2004; Mowles & Briffa 2012), personality (Briffa et al 2008, 2013), crypsis (Briffa & Twyman 2011) and shell selection behaviour (Elwood & Briffa 2001) shows that they rely on a mix of tactile, visual and chemical information in their environment. Due to the established experimental designs that have been used to investigate hermit crab behaviour, they represent an ideal study system for investigating the impacts of ocean noise pollution on marine animal behaviour, driven by this mechanism of distraction. 
In the proposed research the objectives are to determine the extent of behavioural impairment due to distraction effects across tactile, visual and chemical domains. We will use the European hermit crab P. bernhardus as a model study system. Hermit crabs are routinely collected from local field sites. We will use recordings of boat motor noise, played through a hydrophone at 40dB (Chan et al 2010), housed in experimental aquaria. Behavioural data will be collected using The Observer XT 11 event recording software. 
Experiment 1: The effect of noise on tactile information during ‘shell fights’. Hermit crabs engage in agonistic encounters called ‘shell fights’ over the ownership of empty gastropod shells. This involves a distinctive ‘shell rapping’ signal, which the defending crab must assess. We will compare the intensity, duration, escalation patterns and outcomes of shell fights in the presence and absence of boat noise. If noise disrupts the ability of defenders to process the tactile shell rapping information, then weaker defenders may persist in the encounter for longer, wasting energy on contests that they will ultimately loose. 
Experiment 2: The effect of noise on tactile information during ‘shell selection’. Hermit crabs are usually excellent judges of empty gastropod shell size. In this study we will place crabs in shells that are 50% too small and give them the option of moving into anew empty shell of either 55%, 60%, 75% or 100%. In the absence of noise we would expect a crab in a 50% shell to move into a 55% shell, but if noise disrupts the shell assessment -process we would expect the threshold at which shell switching occurs to shift up. 
Experiment 3: The effect of noise on visual information during ‘shell selection’. As well as judging the size of shell, hermit crabs assess the extent to which shells are conspicuous against the substrate. In this experiment we will offer crabs a choice between shells that ‘stand out’ and ‘blend in’. Usually, most crabs will choose a shell that blends in with the background, but if noise disrupts visual assessment we would expect the proportion of crabs choosing the correct type of shell to be lower in the presence of noise. 
Experiment 4: When disturbed by a predator or simulated predation event, hermit crabs rapidly retract into their gastropod shell. In the chemical presence of a predator (e.g. effluent from a tank containing Carcinus maenas) they stay hidden for longer before re-emerging. If sound disrupts responses to chemical information, we would expect the difference in re-emergence between the presence and absence of the predator cue to be less marked in the presence of sound. This study will involve repeated measurements of startle response durations and will also allow the student to address the possibility of habituation to noise (Stahlman et al. 2011) and contribute to the exciting field of ‘animal personality’ research (e.g. Briffa & Weiss 2011), where marine examples are currently understudied. 
A typical hermit crab behaviour experiment takes approximately 6 months for data collection, leaving ample time for analysis and writing up during a 3 year programme consisting of four main experiments. These experiments will be adaptable as the interests of the student develop during the programme. For example, it would be possible to conduct an additional experiment combining two sensory modalities (e.g. visual and chemical) to investigate how attention is partitioned between them and how this is impacted by sound. The second promoter (M. Gammell) is an expert in animal contest theory (Gammell & Hardy 2003) and brings recent interests  in bioacoustics in an aquatic environment (Gammell & O’Brien 2013) so will bring a range of expertise directly relevant to the project. Taken together, these experiments provide the most comprehensive study to date on the ‘distraction’ hypothesis for effects of anthropogenic noise pollution, all within the context of behaviours directly related to individual fitness. As behaviour constitutes a major link between individuals and populations (Candolin & Wong 2012) this study will also provide information about how these effects may scale up to impact on wider ecosystem level processes, such as predator-prey relationships and the transition of resource units through populations (e.g. Briffa & Austin 2008). 
  • Briffa, M. & Austin, M. 2009. Effects of predation threat on the structure and benefits from vacancy chains in the hermit crab Pagurus bernhardus. Ethology 115, 1029-1035.
  •  Briffa, M., Elwood, RW, Dick, J.T.A. 1998. Analysis of repeated signals during shell fights in the hermit crab Pagurus bernhardus.  Proc R Soc Lond B 265,1467-1474. 
  • Briffa, M. & Elwood, R.W. 2000. Cumulative or sequential assessment during hermit crab shell fights: effects of oxygen on decision rules Proc R Soc Lond B 267, 2445-2452.
  • Briffa, M. & Elwood, R.W. 2001. Decision rules, energy metabolism and vigour of hermit-crab fights. Proc R Soc Lond B 268, 1841-1848.  
  • Briffa, M. & Elwood, R.W. 2002. Power of shell-rapping signals influences physiological costs and subsequent decisions during hermit crab fights. Proc R Soc Lond B 269, 2331-2336.
  • Briffa, M. & Elwood, R.W. 2004. Use of energy reserves in fighting hermit crabs. Proc R Soc Lond B 271, 373-379. 
  • Briffa, M. & Mowles, S.L. 2008. Hermit crabs Curr. Biol. 18, R144-R146.
  • Briffa, M., Rundle, S.D. & Fryer, A. 2008. Comparing the strength of behavioural plasticity and consistency across situations: animal personalities in the hermit crab Pagurus bernhardus.  Proc R Soc Lond B 275, 1305-1311. 
  • Briffa M & Twyman C. 2011. Do I stand out or blend in? Conspicuousness awareness and consistent behavioural differences in hermit crabs. Biol. Letts. 7,  330-332. 
  • Briffa M. & Weiss A. 2010. Animal personality. Curr Biol 20, R912-914.
  • Briffa M, Bridger D & Biro PA. In press. How does temperature affect behaviour? Multilevel analysis of plasticity, personality and predictability in hermit crabs. Anim. Behav.
  • Candolin U. & Wong B.M. 2012. Behavioural responses to a changing world, mechanisms and consequences. OUP, Oxford, U.K.
  • Chan, A.A.Y.-H., Giraldo-Perez, P., Smithy, S. & Blumstein, D.T. 2010a. Anthropogenic noise affects risk assessment and attention: the distracted prey hypothesis. Biol Letts 6, 458-461.
  • Chan, A.A.Y.-H., Stahlman, W.D., Garlick, D., Fast, C.D., Blumstein, D.T. & Blaisdell, A.P. 2010b. Increased amplitude and duration of acoustic stimuli enhance distraction. Anim Behav 80, 1075-1079. 
  • Dukas, R. 2004. Causes and consequences of limited attention. Brain Behav Evol 63, 197-210. 
  • Elwood, R.W. & Briffa, M. 2001. Information gathering and communication during agonistic encounters: A case study of hermit crabs.  Adv Stud Behav  30: 53-97. 
  • Gammell M.P. & Hardy I.C.W. 2003. Contest duration: sizing up the opposition? Trends Ecol. Evol. 18,  491-493. 
  • Gammell M.P. & Obrien J.M. 2013. Acoustic communication in aquatic animals: all quiet on the freshwater front? Aquat. Consv. Mar. Fresh. Ecosys. 23, 363–365.
  • Mowles S.L & Briffa M. 2012. Forewarned is forearmed: early signals of RHP predict opponent fatigue in hermit crab shell fights. BEHAVIORAL ECOLOGY 23: 1324-1329.
  • Stahlman, W.D., Chan, A.A.Y.-H., Blumstein, D.T., Fast, C.D. & Blaisdell, A.P. 2011. Auditory stimulation dishabituates anti-predator escape behaviour in hermit crabs (Coenobita clypeatus). Behav. Proc. 88, 7-11.

Expected outcomes
Each proposed experiment would yield data for at least one peer reviewed paper. Typically PhD students working on this study species, using similar techniques, would publish 4-5 papers arising from their PhD. We would expect a proportion of these to be in high impact journals such as Biology Letters, Current Biology or Proceedings of the Royal Society B. The majority of papers would certainly be in ‘top third journals’. We anticipate that the student would give at least one presentation at an international conference during the course of the PhD. Hermit crabs are highly charismatic organisms and research from MB’s lab has achieved public engagement primarily through media coverage, including newspapers, the academic media and national TV (e.g. The Secret Life of Rockpools, BBC4, spring 2013). An additional benefit to this work is that it draws on the complimentary expertise of Briffa & Gammell. Although the partners have collaborated on a recent book (Animal Contests, CUP) we have yet to work together on an experimental study. The collaboration would allow an exchange of expertise and build the capacity for future collaboration between the two institutes.

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