Geographic Range
New Zealand sea lions, also known as Hooker’s sea lions, inhabit the southern stretches
of New Zealand’s territory in the Pacific with colonies reaching as far north as the
Foveaux Straight and as far south as Macquarie Island. However, the vast majority
of breeding occurs among the Auckland Islands, with a scattering of breeding colonies
inhabiting the Campbell Islands. The population is estimated to be between 10,000
and 13,000 total individuals. Although New Zealand sea lions were thought to have
disappeared from the mainland 200 years ago due to human hunting, in 1993 it was reported
that a single sea lion had breed on the mainland peninsula.
- Biogeographic Regions
- oceanic islands
Habitat
New Zealand sea lions are comfortable in a wide range of habitats, from 400 m above
sea level through the hills, forests, and fields of the local islands to dives of
up to 600 m below sea level. Yet, the majority of individuals prefer to remain on
sandy beaches and hunt primarily at depths no greater than 200 m below sea level.
When breeding females will seek shelter in the inland vegetation and, when necessary,
they will hunt mainland birds and their nests.
- Habitat Regions
- polar
- saltwater or marine
- Aquatic Biomes
- coastal
Physical Description
New Zealand sea lion males have a defined mane around their shoulders and a dark brown
or black color. Males reach between 2.4 and 3.5 m in length and weigh between 200
and 400 kg. Conversely, females are a much lighter grey and some are even yellow with
some darker shades around the flippers. Females are also significantly smaller reaching
only between 1.6 and 2 m in length and weighing between 100 and 160 kg. Pups are typically
brown in appearance with young males resembling females until full maturation. This
species also features a very short, blunt head with a length to width ratio of 2:1,
compared to an average ratio for
fur seals and sea lions
of 3:1.
New Zealand sea lions are similar to
Australian sea lions
in appearance, but many differences have surfaced which are used to distinguish New
Zealand sea lions, not only from
Australian sea lions
, but also from most other species of sea lion. It is typical for New Zealand sea
lions to have a deep concave palate (22 mm in males and 14.5 mm in females), a dental
formula of I: 3/2 C: 1/1 Cheek teeth: 6/5, and a smooth cylindrical projection of
the tympanic bulla.
- Other Physical Features
- endothermic
- bilateral symmetry
- Sexual Dimorphism
- male larger
- sexes colored or patterned differently
Reproduction
New Zealand sea lions are polygynous and males are territorial. One dominant male
will occupy a beach in late November and harems of up to 25 females will gather in
December. Other bulls will remain on the perimeter of the territory occasionally challenging
the dominant male. By late January, the harems will break up and the bulls will disperse.
- Mating System
- polygynous
Breeding occurs in New Zealand's summer months and is followed by a gestation period
of about 11 months. Females move to a breeding beach about 2 days before giving birth.
They usually have only one pup at a time and give birth every one to two years. During
their first year, the pups are completely dependent on the mother for food and protection.
At birth males are larger than females, with males weighing in at about 10.6 kg and
females 9.7 kg.
- Key Reproductive Features
- iteroparous
- seasonal breeding
- gonochoric/gonochoristic/dioecious (sexes separate)
- sexual
- viviparous
Body reserves for pups are relatively low at birth. Suckling occurs for eight to nine
days before the mother's first foraging trip, which tends to last for only two days.
A direct influence on pup mortality is male harassment; females move pups to inland
vegetation six weeks after birth, presumably to protect them from adult males.
- Parental Investment
- precocial
- female parental care
Lifespan/Longevity
New Zealand sea lions are not formally kept in captivity and little is known about
their lifespan. However, it is estimated that the maximum lifespan for both males
and females is about 23 years.
Behavior
New Zealand sea lions are a social species, but not migratory. Tracking of females
has shown that they do not travel between the breeding sites in the Auckland Islands
and the Campbell Islands. Their only movement is between the beaches under the control
of the bulls with whom they breed and the birthing beaches.
Male New Zealand sea lions have social hierarchies. The dominant territorial male
has breeding rights leaving juvenile and bachelor males mostly excluded from mating.
- Key Behaviors
- natatorial
- motile
- sedentary
- territorial
- social
- dominance hierarchies
Home Range
In order to feed, New Zealand sea lions might travel up to 175 km from its local coast.
Communication and Perception
New Zealand sea lion communications have not been described, but is widely studied
in their popular relatives,
California sea lions
. For California sea lions, the most common form of communication is vocal. Males,
in particular, use vocal communication to indicate territorial ownership, sexual readiness,
and readiness to fight. Females use vocal cues to communicate alarm and readiness
to suckle to their pups. Pups have an alarm vocalization as well as a vocalization
to indicate hunger.
- Communication Channels
- acoustic
Food Habits
New Zealand sea lions are carnivorous. They predominately eat
arrow squids
, but other common prey include
red cods
,
opalfishes
, other small local fishes,
octopuses
,
rays and sharks
. Most dives are to less than 200 m and last for four to five minutes; maximum dives
reach 600 m. Immature sea lions feed on the same type and size of prey as adults.
There have been reports of New Zealand sea lions traveling on land and hunting
Southern Royal Albatross,
. A number of studies have concluded that New Zealand sea lions often forages and
functions to its physiologic limits; this is thought to limit reproductive output.
- Primary Diet
- carnivore
- Animal Foods
- birds
- fish
- mollusks
- other marine invertebrates
- Foraging Behavior
- stores or caches food
Predation
The only known predators on New Zealand seal lions are
sharks
and
dogs
on the mainland. Humans also hunted New Zealand sea lions, but today New Zealand
laws protect the species.
Ecosystem Roles
New Zealand seal lions are dominant predators. They hunt similarly endangered species,
including the
Southern Royal Albatross
, which worries local scientists and poses an interesting conundrum.
New Zealand seal lions have a mutualist relationship with the
red-billed gull
. This bird will perch on the back of New Zealand seal lions picking the blowflies
and other insects from the lion’s back and head. This behavior is similar to that
of birds and cattle.
- red-billed gull ( Larus novaehollandiae )
Economic Importance for Humans: Positive
There are no known positive effects of New Zealand seal lions on humans.
Economic Importance for Humans: Negative
There are no known adverse effects of New Zealand seal lions on humans.
Conservation Status
According to the New Zealand Department of Conservation, New Zealand seal lions are
listed as critical, while IUCN lists the species as vulnerable. New Zealand is highly
concerned about New Zealand seal lions, because of interactions with local fishing
vessels. They rely on
arrow squid
for food, but humans fish for this squid, as well. Similar to dolphin interactions
with tuna fishing, New Zealand seal lions tend to be a common incidental catch of
squid fishermen. The New Zealand Government has put limits on the numbers of New Zealand
seal lions that can be caught in fishing nets. Once this limit is reached, the fishery
must close operations for the remainder of the season.
Another cause for conservation concern for New Zealand seal lions are bacterial epidemics.
Each epidemic takes out hundreds of adults and pups. Scientists must take this into
consideration when contemplating further management plans for this species, because
the population is already limited and has a restricted range.
Additional Links
Contributors
David Ferland (author), Michigan State University, Barbara Lundrigan (editor), Michigan State University.
- oceanic islands
-
islands that are not part of continental shelf areas, they are not, and have never been, connected to a continental land mass, most typically these are volcanic islands.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- polar
-
the regions of the earth that surround the north and south poles, from the north pole to 60 degrees north and from the south pole to 60 degrees south.
- saltwater or marine
-
mainly lives in oceans, seas, or other bodies of salt water.
- coastal
-
the nearshore aquatic habitats near a coast, or shoreline.
- polygynous
-
having more than one female as a mate at one time
- iteroparous
-
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
- seasonal breeding
-
breeding is confined to a particular season
- sexual
-
reproduction that includes combining the genetic contribution of two individuals, a male and a female
- viviparous
-
reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.
- young precocial
-
young are relatively well-developed when born
- female parental care
-
parental care is carried out by females
- natatorial
-
specialized for swimming
- motile
-
having the capacity to move from one place to another.
- sedentary
-
remains in the same area
- territorial
-
defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement
- social
-
associates with others of its species; forms social groups.
- dominance hierarchies
-
ranking system or pecking order among members of a long-term social group, where dominance status affects access to resources or mates
- acoustic
-
uses sound to communicate
- tactile
-
uses touch to communicate
- acoustic
-
uses sound to communicate
- chemical
-
uses smells or other chemicals to communicate
- stores or caches food
-
places a food item in a special place to be eaten later. Also called "hoarding"
- carnivore
-
an animal that mainly eats meat
- piscivore
-
an animal that mainly eats fish
- molluscivore
-
eats mollusks, members of Phylum Mollusca
- endothermic
-
animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
- bilateral symmetry
-
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
References
Bell, B. 2008. Mutualistic and opportunistic foraging by red-billed gull ( Larus novaehollandiae ) around Hooker's sea lion ( Phocarctos hookeri ). Notornis , 55: 224-225.
Charteris, M., P. Moore, E. Larsen. 2008. Notes on New Zealand mammals 8. Predation on nesting southern royal albatrosses Diomedea epomophora by New Zealand sea lion Phocarctos hookeri . New Zealand Journal of Zoology , 35: 201-204.
Clark, J. 1873. On the eared seals of the Auckland Islands. Proceedings of the Zoological Society of London , 1873: 750-760.
Kahui, V. 2011. A bioeconomic model for Hooker’s sea lion bycatch in New Zealand. The Australian Journal of Agricultural and Resource Economics , 56: 22-41.
King, J. 1960. Sea-lions of the genera Neophoca and Phocarctos . Mammalia , 24: 445-456.
Louise Chilvers, B., B. Robertson, I. Wilkinson, P. Duignan. 2007. Growth and survival of New Zealand sea lions, Phocarctos hookeri : birth to 3 months. Polar Biol , 30: 459-469.
Maloney, A., B. Louise Chilvers, M. Haley, C. Muller, W. Roe, I. Debski. 2009. Distribution, pup production and mortality of New Zealand sea lion ( Phocarctos hookeri ) on Campbell Island/Motu Ihupuku, 2008. New Zealand Journal of Ecology , 33/2: 97-103.
Meynier, L., D. Mackenzie, P. Duignan, B. Louise Chilvers, P. Morel. 2009. Variability in the diet of New Zealand sea lion (Phocarctos hookeri) at the Auckland Islands, New Zealand. Marine Mammal Science , 25/2: 302-326.
Peterson, R., G. Bartholomew. 1969. Airborne vocal communication in the California sea lion, Zalophus californianus . Animal Behavior , 17: 17-24.
2010. "New Zealand Sea Lion" (On-line). New Zealand Department of Conservation. Accessed March 12, 2012 at http://www.doc.govt.nz/conservation/native-animals/marine-mammals/seals/new-zealand-sea-lion-rapoka-whakahao/ .