The holotypes of the subspecies E. m. variabilis[8] and Eudyptula minor chathamensis[9] are in the collection of the Museum of New Zealand Te Papa Tongarewa.

The head and upper parts are blue in colour, with slate-grey ear coverts fading to white underneath, from the chin to the belly.

The dark grey-black beak is 3–4 cm long, the irises pale silvery- or bluish-grey or hazel, and the feet pink above with black soles and webbing.

Using ancient-DNA analysis and radiocarbon dating using historical, pre-human, as well as archaeological Eudyptula remains, the arrival of the Australian species in New Zealand was determined to have occurred roughly between AD 1500 and 1900.

The decrease of E. minor was most likely due to anthropogenic effects, such as being hunted by humans as well as introduced predators,[15] including dogs brought from overseas.

It has been determined using multilocus coalescent analyses that the population of Eudyptula novaehollandiae in Otago arrived less than 750 years ago, more recently than previously estimated.

[18] Despite nesting on the shore, little penguins forage at sea and feed on a diet ranging from small schooling fish, to cephalopods, krill, and microzooplankton.

Important little penguin prey items include arrow squid, slender sprat, Graham's gudgeon, red cod, and ahuru.

[22] Little penguins feed by hunting small clupeoid fish, cephalopods, and crustaceans, for which they travel and dive quite extensively,[23][24] including to the sea floor.

Foraging success appears to stabilise selection for middle-aged penguins, as feeding is a learnt behaviour but also requires good physical condition.

[27] During the breeding season, parents are restricted to a short foraging area close to their nest and are therefore vulnerable to small regional changes.

[30] La Niña events increasing the sea surface temperature along the New Zealand coastline cause prey such as schooling fish and krill to either become more regionally scarce or migrate to new habitats.

[23] Graham's Gudgeon once dominated the diet of the Oamaru colony of Eudyptula minor, however in 1995 the availability of the species dropped from 20% in December to 0% in January the following year.

There is no evidence to suggest this is an established behaviour within Eudyptula minor, however double broods are occasionally noticed among the colonies in the Kaikoura coastline.

[35] Warmer sea surface temperature in summer and autumn correlated with earlier laying of first clutch of eggs increasing the chances of double brooding.

[32] In contrast, in New Zealand it was observed that during the La Niña phase of the El Niño Southern Oscillation when colder temperature water was brought to the surface, there was a delay in the onset of breeding for Eudyptula novaehollandiae, thus resulting in a lower incidence of double brooding in the Otago colonies.

[26] Particularly , In order to survive Eudyptula minor adapt to these constraints by increasing the plasticity and variability in their foraging behaviour, such as spatial, age, or diet based segregation, during breeding season when energy demands for both parents and chicks are at their highest.

[26] Research conducted on the Philip Island colony found the spatial segregation of foraging behaviour was primarily determined by age rather than biological sex.

[26] Introduced mammalian predators present the greatest terrestrial risk to little penguins and include cats, dogs, rats, and particularly ferrets and stoats.

[45][46] Oil spills are the most common cause of the little penguins being admitted to the rehabilitation facilities at Phillip Island Nature Park (PINP).

Behavioural traits such as reluctancy to abandon nests and emerging mostly during daylit hours is thought to be some of the main reasons for increased vulnerability in the future.

[48] The threats it provides include nest and habitat distruption, as well as deadly to eggs and individuals, despite this Eudyptula minorappears to show no fear towards fire when directly exposed.

A large fire in Marion Bay, South Australia in 1994 saw the loss of two key plant species; introduced marram grass Ammophila and coastal wattle A.sophorae.

[41] The species is not considered endangered in New Zealand, with the exception of the white-flippered subspecies found only on Banks Peninsula and nearby Motunau Island.

[51] Protestors have opposed the development of a marina at Kennedy Point, Waiheke Island in New Zealand for the risk it poses to little penguins and their habitat.

Despite these efforts, this mainland colony was met with additional challenges from threats from wild dogs and foxes, to lack of available local prey.