Protecting Porpoises: World Animal Day’s Hidden Heroes

As we celebrate World Animal Day on October 4th, Ocean Conservationist Gemma takes a look at some of the ocean’s most enigmatic and often overlooked inhabitants- porpoises.

World Animal Day is a global event dedicated to raising awareness about animal welfare and promoting the protection of all species. While they might not always make the headlines like their whale and dolphin relatives, porpoises are truly amazing and equally deserving of our attention and protection. To celebrate World Animal Day, let’s explore some interesting facts about porpoises and the conservation threats they are facing.

Are Porpoises the Same as Dolphins?

No, they are not! Although the terms “dolphin” and “porpoise” are sometimes used interchangeably, they refer to different groups. Porpoises belong to the Phocoenidae family, whereas dolphins are part of the Delphinidae family.

There are seven known species of porpoise:

• Harbour porpoise

• Dall’s porpoise

• Vaquita

• Burmeister’s porpoise

• Spectacled porpoise

• Indo-Pacific finless porpoise

• Narrow-ridged finless porpoise

Both dolphins and porpoises are part of the suborder Odontoceti, which means that porpoises are also toothed whales. Porpoises can be found from the Arctic to the tropics and also in freshwater rivers (1). In comparison to dolphins, less is generally known about porpoises partly due to their more elusive nature (1) and inconspicuous surface activity, as they rarely engage in the aerial displays that dolphins do. This makes them difficult to detect and study. They also generally shy away from boats. However, Dall’s porpoises are an exception as they can often be seen bow-riding and even “snout riding”, where they ride the waves created by a large whale’s head! (2). Generally speaking, porpoises are smaller than dolphins and have a rounded, blunt snout rather than a prominent beak that is seen in many species of dolphin (there are exceptions such as Māui dolphins and Hector’s dolphins which lack an obvious beak).

Porpoises tend to have stout, stocky bodies and triangular dorsal fins compared to dolphins which are sleeker and tend to have a curved dorsal fin (again, there are exceptions, but these are some general ways to help tell them apart!). Another interesting difference is their teeth. While oceanic dolphins have conical teeth, porpoises have flat, spade shaped teeth (3). As with other toothed whales, porpoises have the ability to echolocate, but their vocal behaviour differs to dolphins as they are not thought to produce whistles. It has been suggested that structural differences in their blowholes could prevent them from generating whistles, but more research is needed to gain clarity on this. Although much of their social behaviour remains poorly understood, porpoises are generally found in much smaller groups than dolphins. Initially thought to be less social than dolphins, tagging data has revealed that harbour porpoises are more social than previously suggested, and remain in acoustic contact with other members of their group (1).

Conservation Threats

Porpoises face a range of human-induced threats including entanglement and bycatch in fisheries, chemical pollution, and noise pollution. In Japanese waters, Dall’s porpoises are also intentionally hunted for human consumption. Due to their preference for prey also targeted by fisheries and their smaller body sizes, porpoises are particularly susceptible to bycatch. This can pose a significant threat and contribute to severe population declines, with the most notable example being the critically endangered vaquita (which translates as “little cow”). Sadly, due to continued unsustainable rates of bycatch, there are thought to be only around 10 of these little porpoises left, and their future is uncertain. The vaquita’s plight starkly illustrates the potential for catastrophic impacts of bycatch on a population. The Iberian harbour porpoise, and the Baltic Sea harbour porpoise (critically endangered) are also seriously affected by bycatch, and this has been linked to their population declines (4). Bioaccumulation of polychlorinated biphenyls (PCBs) has been suggested as a contributing factor to reproductive failure in harbour porpoises, which poses an additional threat (4, 5)

How Does ORCA Protect Porpoises?

By continuously monitoring populations of porpoises (and other cetaceans), ORCA’s data collection is vital to map out important habitats, identify key hotspots, and establish which populations and species are the most at risk. Identifying areas of significant overlap between human and cetacean activity enables ORCA to implement effective conservation measures to mitigate the impacts of human activity in high-risk areas. For example, ORCA’s data was used to help inform the designation of 33 new Important Marine Mammal Areas (IMMA’s). This helps to identify whether important habitats are included under existing protective legislation, and if not, this data provides evidence to advocate for better protection within these areas-including for the critically endangered Baltic Sea harbour porpoise.

During 2022-2023, ORCA (along with colleagues at WDC, HIS, and Coalition Clean Baltic) submitted a joint proposal to ASCOBANS and CMS as a call to action for stronger protection of both the Baltic and Iberian harbour porpoise populations. As a result of this collaborative effort, the CMS member states submitted a proposal to grant the harbour porpoise the highest protection status, which means that targeted conservation measures can be implemented (read more here).

ORCA’s data informs targeted conservation efforts for cetacean populations. However, there remains significant gaps in knowledge, making our ongoing work more important than ever. It is vital that we continue to improve our understanding of cetacean habitat use, behaviour, and areas of high risk.

Although porpoises don’t get the spotlight as often as whales and dolphins, they still face a range of threats and urgently need our help. They face many of the same threats as their more famous relatives- such as bycatch, habitat degradation, and pollution-yet their struggle goes largely unnoticed by the general public (4). With so few people aware of the challenges porpoises face (or that they even exist!), fighting for their conservation becomes even more critical. Porpoises don’t have the same public image as well-known cetaceans like killer whales and bottlenose dolphins, so we must be their voice and ensure that we keep porpoises in the public eye to help secure their future.

Title image credit: Andy Gilbert

References

1. Teilmann, J. and Sveegaard, S., 2019. Porpoises the World over: Diversity in behavior and ecology. Ethology and Behavioral Ecology of Odontocetes, pp.449-464.

2. Jefferson, T.A., Dahlheim, M.E., Zerbini, A.N., Waite, J.M. and Kennedy, A.S., 2019. Abundance and Seasonality of Dall’s Porpoise (Phocoenoides dalli) in Southeast Alaska.

3. Whales, D., 1995. Porpoises. M. Carwardine & M. Camm.

4. Carlén, I., Nunny, L. and Simmonds, M.P., 2021. Out of sight, out of mind: how conservation is failing European porpoises. Frontiers in Marine Science, 8, p.617478.

5. Murphy, S., Barber, J.L., Learmonth, J.A., Read, F.L., Deaville, R., Perkins, M.W., Brownlow, A., Davison, N., Penrose, R., Pierce, G.J. and Law, R.J., 2015. Reproductive failure in UK harbour porpoises Phocoena phocoena: legacy of pollutant exposure?. PLoS One, 10(7), p.e0131085.