The mysterious attraction of the Hutt River to crabeater seals

In late March 2015, a crabeater seal swam up the Hutt River (which flows into Wellington Harbour) and died. It was a remarkable occurrence – the crabeater seal is an Antarctic species rarely recorded in New Zealand – but no-one realised at the time that this was precisely the place in New Zealand where a crabeater seal was likely to be found.

Crabeater seal beside the Hutt River, March 2015. Image: Anneke Mace, Department of Conservation

Crabeater seal beside the Hutt River, March 2015. Image: Anneke Mace, Department of Conservation

Finding out how many crabeater seals had reached New Zealand, and where and when they had been found, turned out to be more complicated than I had expected. Birdwatchers are very good at keeping records of vagrant birds that reach New Zealand, and publishing their findings (e.g. in the journal Notornis, or the magazine New Zealand Birds, both published by Birds New Zealand), but there is no equivalent society, magazine or journal for vagrant seals.

Weddell seal, Napier, June 2007. Image: Department of Conservation

Weddell seal, Napier, June 2007. Image: Department of Conservation

Crabeater seals belong to the true seals, of which there are five species in the Southern Hemisphere. All five species occur in New Zealand waters, and I have listed them here in their frequency of occurrence:

  • Southern elephant seal (Mirounga leonina)
  • Leopard seal (Hydrurga leptonyx)
  • Crabeater seal (Lobodon carcinophaga)
  • Weddell seal (Leptonychotes weddellii)
  • Ross seal (Ommatophoca rossii)
Ross seal, Paekakariki, September 2002. Image: Department of Conservation

Ross seal, Paekakariki, September 2002. Image: Department of Conservation

All five are readily distinguished from fur seals and sea lions (the most common seals seen on New Zealand coasts) by their slug-like body shape. True seals are unable to rotate their pelvis forward, and so drag their tails behind them. In contrast, fur seals and sea lions can raise their bodies off the ground and walk, gallop or climb with ease.

New Zealand fur seal. Image: Colin Miskelly, Te Papa

New Zealand fur seal. Image: Colin Miskelly, Te Papa

Elephant seals breed in small numbers on Antipodes Island and Campbell Island (both in the New Zealand subantarctic) and regularly reach mainland shores. A few pups have even been born along the east coast of the South Island and on the Wairarapa coast – most recently one at Timaru in September 2015.

Male southern elephant seal. New Zealand fur seal. Image: Colin Miskelly

Male southern elephant seal. Image: Colin Miskelly

The four remaining species all breed on Antarctic sea-ice, but leopard seals regularly swim north, with a few reaching New Zealand shores every year, even as far north as Northland.

Leopard seal. New Zealand fur seal. Image: Colin Miskelly, Te Papa

Leopard seal. Image: Colin Miskelly, Te Papa

The three remaining species are much rarer visitors to our shores, but it took a bit of sleuthing to discover just how rare they are. The obvious starting point was the 610 page Handbook of New Zealand Mammals (2nd edition, published in 2005). Unfortunately the only relevant information contained therein was that “Crabeater seals are also seen occasionally in New Zealand…waters” (p.253), with no hint that Weddell seals or Ross seals ever roam so far north. The next place to check was museum holdings, which turned up three earlier crabeater seals and two Weddell seals here at Te Papa, a Weddell seal at Auckland Museum, and a crabeater seal at each of Whanganui Regional Museum and Canterbury Museum. The Department of Conservation marine mammal stranding database contained information on one animal of each species (all additional to the museum holdings). Information on two further animals (a crabeater seal and a Weddell seal) was found in old Marine Department files held by Archives New Zealand. When added to the animal found in March 2015, this produced a total of 14 verifiable records of the three species: eight crabeater seals, five Weddell seals and a single Ross seal.

New Zealand crabeater seal records
1885 Whanganui River Heads Whanganui Museum
Apr 1916 Petone Beach, Wellington Te Papa
Jun 1933 Petone Beach & Hutt River, Wellington Te Papa
Jul 1934 Petone Beach & Hutt River, Wellington Te Papa
Aug 1949 Avon-Heathcote estuary, Christchurch Canterbury Museum
Dec 1963 Lyall Bay & Petone Beach, Wellington
Mar 2011 South Bay, Kaikoura
Mar 2015 Island Bay & Hutt River, Wellington Te Papa
New Zealand Weddell seal records
Jun 1926 Titahi Bay, Wellington Te Papa
Jun-Jul 1937 Wellington Harbour & Napier
Aug 1948 Muriwai, Auckland Auckland Museum
1964 Haldane River estuary, Southland Te Papa
Jun 2007 Mahia Beach & Napier
New Zealand’s only Ross seal record
Sep-Oct 2002 Paekakariki, Kapiti coast

The most striking feature of these 14 records is their geographical spread – or lack thereof. Eight of the animals were reported from the Wellington region (one of the Weddell seals later swam to Napier), and five of the eight crabeater seals were reported from the Hutt River or the adjacent Petone Beach.

Verified records of three species of vagrant Antarctic seal from New Zealand. Circles = crabeater seals, with open circles showing second locations for two animals, squares = Weddell seals, with open squares showing second locations for two animals, triangle = Ross seal. A version of this map was published in NZ J Marine & Freshwater Research Vol 49, part 4 (reference given below).

Verified records of three species of vagrant Antarctic seal from New Zealand. Circles = crabeater seals, with open circles showing second locations for two animals, squares = Weddell seals, with open squares showing second locations for two animals, triangle = Ross seal. A version of this map was published in NZ J Marine & Freshwater Research Vol 49, part 4 (reference given below).

There are at least two plausible hypotheses for the cluster of vagrant Antarctic seal records around Wellington. Maybe these seals turn up all round New Zealand, but are undiscovered, unrecognised or unreported at most sites where they come ashore. Wellington not only has a higher population density than most parts of New Zealand, but for the past century there have been scientists based at the national museum or the national offices of relevant government departments who knew how to identify the different Antarctic seals. The second theory is that as these animals were swimming north from Antarctica, the angle of the South Island directed them towards the south coast of the North Island, where they either came ashore on the south coast (Island Bay or Lyall Bay), or they swam into Wellington Harbour, where their northward passage was blocked by Petone Beach – or they could keep on swimming up the Hutt River…

Crabeater seal, Melling, Lower Hutt, July 1934. Image: John Salmon, Te Papa image MA_A.000173

Crabeater seal, Melling, Lower Hutt, July 1934. Image: John Salmon, Te Papa image MA_A.000173

Time will tell which of these hypotheses is more plausible. The ubiquitous ownership of cellphones (with cameras) plus website forums that allow images to be shared and discussed (e.g. NatureWatchNZ) means that unusual seals that turn up anywhere in New Zealand are far more likely to be correctly identified and recorded than was the case twenty or one hundred years ago.

Hutt River mouth looking across to Petone Beach. If you wish to see a crabeater seal in New Zealand, your best bet is to visit this site, and wait approximately 25 years. Image: Colin Miskelly, Te Papa

Hutt River mouth looking across to Petone Beach. If you wish to see a crabeater seal in New Zealand, your best bet is to visit this site, and wait approximately 25 years. Image: Colin Miskelly, Te Papa

With thanks to the Department of Conservation for permission to reproduce the first three images.

Further reading

A crabeater seal – a long way from home

Miskelly, C.M. 2015. Records of three vagrant Antarctic seal species (Family Phocidae) from New Zealand: crabeater seal (Lobodon carcinophaga), Weddell seal (Leptonychotes weddellii) and Ross seal (Ommatophoca rossii). New Zealand Journal of Marine and Freshwater Research 49: 448-461.

 

 

4 Responses

  1. Susie Brown

    In the 1950s during a holiday at Shag Point north if Dunedin, an elephant seal seemed to have taken up residence on the beach. Mum claimed that they came ashore only if they were very ill. It died the next day.

    Reply
    • Colin Miskelly

      Hi Susie
      Thanks for your comment.
      Elephant seals moult their skin and fur every year, mainly during the late summer months, during which each animal has to stay on shore for about a month. This is energetically expensive, and so animals that are old or sick often perish during their moult. In addition to the moulting period, there have been several long-staying individuals around New Zealand that have been in apparent good health, yet have chosen to return to the same stretch of coast for days at a time over periods of many months or years.
      Regards
      Colin

  2. Stuart Nicholson

    Very interesting Colin .. but 25 years wait at the Hutt River mouth? I would have to take more than a picnic lunch 😉

    Reply
    • Colin Miskelly

      Thanks for your comments Stuart
      With a mobile phone and multiple fast-food delivery options in Petone, I am sure you will manage. Please give me a call when you find one!
      Cheers
      Colin

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