In a world that is increasingly perturbed by humans, the need to understand ecosystems is urgent. Attaching measuring devices to wild animals is often the only way to acquire vital life‐history information on larger, charismatic species, and on cryptic species that do not lend themselves to observation. However, the ethics of acceptable practice for attached devices are poorly defined. Here, we consider the need for further research and attempt to identify a system that allows animal restraint practices and device‐induced effects to be quantified and monitored, so that ethics committees can have a defined scale on which to base decisions.

A fourth production region for the globally important Antarctic bottom water has been attributed to dense shelf water formation in the Cape Darnley Polynya, adjoining Prydz Bay in East Antarctica. Here we show new observations from CTD-instrumented elephant seals in 2011–2013 that provide the first complete assessment of dense shelf water formation in Prydz Bay. After a complex evolution involving opposing contributions from three polynyas (positive) and two ice shelves (negative), dense shelf water (salinity 34.65–34.7) is exported through Prydz Channel. This provides a distinct, relatively fresh contribution to Cape Darnley bottom water. Elsewhere, dense water formation is hindered by the freshwater input from the Amery and West Ice Shelves into the Prydz Bay Gyre. This study highlights the susceptibility of Antarctic bottom water to increased freshwater input from the enhanced melting of ice shelves, and ultimately the potential collapse of Antarctic bottom water formation in a warming climate.

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