Shoals: island where Dartmouth can study marine life

Dartmouth Undergraduate Journal of Science

Shoals: island where Dartmouth can study marine life

Leah Valdes 1and Mark E. Laidre 2

1 Biology major (’18) writing thesis based on research at Shoals


2 Assistant Professor in Biological Sciences


Oceans cover over 70 percent of Earth’s surface, and yet our scientific understanding of the behavior, ecology, and evolution of marine organisms is far less than that of their terrestrial counterparts. Much therefore remains to be discovered about the complexities of marine life. And not just with a biological lens: interdisciplinary tools and perspectives from chemistry, physics, mathematics, and engineering are invaluable, if we are to explore the full depths of life in the ocean.

While Dartmouth has on-campus opportunities to study marine systems in the classroom, there is nothing like conducting field work in marine ecosystems. Here we provide a short narrative about marine research we conducted during summer 2017 at Shoals Marine Laboratory. Located in the Gulf of Maine, 6 miles off the coast, Shoals can be easily reached with just a 2-hour drive from Hanover to Portsmouth followed by a 1-hour ferry ride to Appledore Island in the Isles of Shoals. While readily accessible, the pristine surroundings of Shoals feel a world away from the bustle of the mainland (Picture 1, to the left). Indeed, the location of this field site is ideally suited for marine research, boasting well-equipped laboratories, teaching classrooms, helpful research staff, dorms, and a kitchen whose cooks ensure all who stay on the island are well-fed. The island, which is jointly overseen by Cornell University and University of New Hampshire, has been a dedicated field station for over 50 years, with countless long-term research projects, as well as a wide selection of undergraduate classes offered during the summers.


Only recently though has Dartmouth established an earnest foothold on Shoals. After completing our first summer of research on Shoals, a Dartmouth alum (Bill Kneisel ’69) generously gave Dartmouth a donation, which funds continued research on Shoals by Dartmouth students and faculty for the next 5 years. An important part of our motivation in writing this piece is therefore to highlight the amazing opportunity that Shoals presents for those with an interest in studying marine life in the field.

Our own interest in Shoals centers on animal behavior. For one of us (ML) this interest was also, in part, an act of repentance: ML had never visited Shoals when he was a Cornell undergrad, despite many Shoals research opportunities being advertised across campus[1]. A decade after graduating though, ML atoned for this foolish oversight and set foot on Shoals in September 2016, just as he was starting a faculty appointment at Dartmouth. After a few days of pilot observations on Shoals he was sold on this island as an ideal local research site.

We formally launched a Dartmouth project on Shoals from May to September 2017, collecting data for LV’s undergraduate thesis. The key question of this research was: how do animals find resources that are rare in space and time? Many species must solve this dilemma across a variety of landscapes, and particularly in complex environments, such as beneath the ocean, there exists substantial spatio-temporal uncertainty in where and when new resources will become available. The organisms we sought for an answer to this question were subtidal hermit crabs, Pagurus acadianus (Picture 2, to the right), ideal creatures for experimental study because they are critically reliant on resources, specifically empty shells, which are exceedingly rare and hard to come by (Laidre 2011).

To answer our question, we donned snorkels and flippers, dodged some aggressive gulls and poison ivy, and headed into the ocean to see for ourselves how hermit crabs were solving this problem. We began our research by systematically sampling the subtidal to quantify shell availability in space and time (see ‘Dartmouth Shoals’ videos on YouTube). Empty shells were indeed rare spatially. Furthermore, powerful tidal forces moved shells, or even buried them altogether, thereby increasing temporal uncertainty. How then can hermit crabs locate their critical resources? One potential solution is to exploit as information the cues incidentally produced when empty shells are created. Over hundreds of millions of years, many predatory species have evolved specialized abilities to prey upon snails. While some of these predators crush the shell to access the snail’s flesh, others like starfish (Picture 3a, to the left) and large predatory gastropods (Picture 3b, below and to the right), avoid having to break the shell: instead they secrete specialized enzymes, which degrade the snail’s flesh, allowing the predator to digest the snail externally, while leaving the shell intact. Such non-destructive predation should generate chemical cues as by-products, cues which, in theory, could serve as information to hermit crabs about the imminent availability of new shells. We ‘fleshed out’ this hypothesis by simulating non-destructive predation events, first treating mollusk flesh with natural enzymes and then conducting controlled field experiments in which we tested the attractiveness of the chemical products to hermit crabs. In our experiments, hermit crabs flocked most to the sites containing enzyme-treated flesh. Our results (Valdes and Laidre 2018, in review) thus suggest that animals can resolve the problem of spatio-temporal uncertainty by exploiting long-distance chemical cues, within a complex web of ecological relationships involving predators and prey.




While these results have answered our original question, many fascinating questions remain. We look forward to exploring this topic and study system further during continued research on Shoals in summer 2018. Some of our follow-up questions include: What precise molecules act as information beacons to individuals searching for shells? How and why does geographical variability in the ‘biological market’—the supply and demand of shells—impact individuals’ sensitivity to this information? And might anthropogenic noise or global change be fundamentally altering the underlying ecological and evolutionary relationships?


These are just a few of countless scientific questions that can be asked at Shoals, and most specifically on hermit crabs. Admittedly, it would be a shell-shock to us to learn that not every scientist is absorbed by hermit crabs. Nevertheless, it should be pointed out that a wealth of additional marine life is present on Shoals, from deep-sea sharks and intertidal barnacles to nesting colonies of seabirds and harbor seals. LV is excited to conduct further research on Shoals in summer 2018 and imagines many other undergrads would likewise find the experience intellectually rewarding. If you have an interest in marine life and think that Shoals might be a place you would like to conduct research or take classes, then consider reading more about the site:


Whatever you decide, don’t be like one of us (ML) and take a decade before finally exploring Shoals.


Note: A formal application process for summer research opportunities is presently being created by a committee within the Department of Biological Sciences. This application process will be advertised in future years to encourage a diverse group of researchers from Dartmouth to study on Shoals. We hope other Dartmouth faculty and students will take advantage of this unique site, which is host to countless research opportunities, for biologists and beyond.



Laidre, M.E. 2011. Ecological relations between hermit crabs and their shell-supplying gastropods: constrained consumers. Journal of Experimental Marine Biology and Ecology397: 65-70.

Valdes, L. and Laidre, M.E. 2018 (in review). Resolving spatio-temporal uncertainty in rare resource acquisition: smell the shell. Evolutionary Ecology

[1]Notably, another Biological Sciences faculty member at Dartmouth (Professor Mary Lou Guerinot) didhave the good sense to explore Shoals back when she was a Cornell undergrad.

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