Fall Asleep While Learning About The Naultinus & Gecko

Welcome to the I Can't Sleep Podcast,

Where I read random articles from across the web to bore you to sleep with my soothing voice.

I'm your host,

Benjamin Boster,

And today's episode is from a Wikipedia article titled Naltonus.

Naltonus is a genus of geckos that are endemic to New Zealand.

On account of their striking coloration,

Species in the genus Naltonus are commonly known as green geckos.

There are nine described species in the genus.

Species in the genus share a number of traits that set them apart as quite different from the rest of the world's 2,

000-odd gecko species,

Which are generally brown in color,

Oviviparous,

Short-lived,

And nocturnal.

In contrast,

Naltonus are green,

With the exception of males in two South Island species,

Which exhibit sexual dimorphism and coloration,

Oviviparous,

Live up to 30 years or more,

And are strictly diurnal.

New Zealand has a temperature,

Maritime climate,

And in terms of distribution,

Naltonus is one of the southernmost gecko genera in the world.

Some species live in habitats in the South Island,

Which receive regular snowfall in winter.

Animals in this genus possess several physiological and behavioral adaptations to cope with these periods of low temperatures and adverse weather.

While historically widespread and quite common in areas of native forests all over the country,

All species in this genus are of conservation concern in the present day.

The following nine described species are recognized as being valid.

Naltonus elegans grey,

1842,

Auckland green gecko.

Naltonus flavorictus,

Hitchell,

Nielsen,

Lysakht,

And Bower,

2021.

Hapuri green gecko,

North Cape green gecko,

Yellow-lipped green gecko.

Naltonus chemeus,

Jeweled gecko.

Naltonus grey-eyed bell,

1843,

Northland green gecko,

Grazed tree gecko.

Naltonus manaconus,

Marlborough green gecko,

Northern tree gecko.

Naltonus punctidus grey,

1843,

Wellington green gecko.

Naltonus rudus,

Rough gecko,

Natural tree gecko.

Naltonus stellatus hudden,

1872,

Nelson green gecko,

Starry tree gecko.

Naltonus tuberculatus,

West Coast green gecko,

Lewis Pass green gecko.

Defining what constitutes a species among different populations within this genus has proved difficult and is still a matter of some scientific debate.

Genetic evidence suggests that all nine species share an ancestor,

Which is very recent in deep time terms,

And that hybridization between them is quite common.

All species will interbreed in the wild,

Which has led some biologists to reject the notion of multiple Naltonus species,

And to instead view each species as a separate race or subspecies of a single,

Very widespread species of this genus.

However,

There are many clear differences between recognized species and coloration,

Breeding times,

And even scale morphology.

Many neighboring species have slightly different mating seasons and behavior,

Which is thought to explain why the species maintain their differences despite strong reproductive compatibility.

These differences are the basis for the present consensus in the scientific community that Naltonus is constituted of nine species instead of nine races of a single species.

Genetically speaking,

The jeweled gecko of the Southern South Island is the most genetically distinct of the recognized species.

In fact,

It is thought that this species is the one that is ancestral to all other species in the genus.

There are three distinct populations of N.

Gemmius in the Southland,

Otago,

And Canterbury,

Differentiated by coloration and the time of their breeding seasons.

In addition to recognizing G.

Gemmius as one of a number of separate species within the genus,

Some biologists think that the three different populations of this species should be elevated to subspecies status to place more emphasis on their conservation management.

Naltonus species are commonly known as green geckos in New Zealand for their striking bright green coloration.

In addition,

They are diurnal,

Which allows them to take advantage of warmer daytime temperatures.

Both of these features are shared only with the day geckos of Madagascar.

Almost every other type of gecko in the world is nocturnal,

And brown or gray in color.

All Naltonus are arboreal,

And though most of them are predominantly green,

Their skin patterns are known to be plain,

Spotted,

Or striped.

Occasionally,

Individuals of an overall lemon-yellow color are encountered.

This is rare genetic color morph similar to albinism.

The distinctive green coloration is almost universally predominant,

With the two exceptions of male N.

Rudus,

As well as males of some populations of the Canterbury form of N.

Gemmius,

Which are sexually dichromatic.

While females are green,

The males of N.

Rudus are gray with white and brown splotches,

And in Canterbury,

N.

Gemmius females are always predominantly green,

As compared to the gray,

Brown,

Or white males.

The inside of the mouth,

Which is revealed in a threat display in some species,

Is deep blue,

Orange,

Pink,

Or red.

The broad,

Fleshy tongue,

Which has a major function in cleaning the transparent scales which cover the eyes,

Is also brightly colored.

Depending on the species,

It is red,

Orange,

Pink,

Yellow,

Or black.

The ears of New Zealand geckos appear as small openings on the side of the head,

Behind the eyes,

And the eardrum is visible a short distance inside this opening.

N.

Species,

And indeed New Zealand lizards in general,

Are very conservative in their evolutionary development of scales.

Most have the standard gecko-type scales which are small and granular,

Giving the skin a dull,

Velvety appearance.

The two exceptions to this rule are two South Island members of the genus,

The rough gecko,

N.

Rudus,

And,

To a lesser extent,

The Marlborough green gecko,

N.

Manachanus.

The rough gecko has enlarged conical scales,

Which are both significantly wider and which protrude much further from the body than ordinary scales.

These enlarged scales are scattered all over the body except for the underside of the animal.

The Marlborough green gecko also has enlarged scales,

But they are confined to the dorsal,

Pelvic area,

And sometimes even in rows along the side of the animal.

In any case,

They are never found over all upper surfaces of the body as in the rough gecko.

All Naldinus species also possess very long,

Finely tapered,

Strongly prehensile tails,

Which they use as a fifth limb for grasping when they climb among the twigs and leaves of their arboreal habitat.

They can hang by their tails if necessary.

They also have comparatively slender toes,

Another adaptation to their arboreal lifestyle.

The arboreal Naldinus use their toes in a grasping action on twigs and leaves,

But there is some lamellar function as well.

The nine described species of Naldinus are found throughout the North and South Islands of New Zealand and on a number of offshore islands.

Historically,

Naldinus species live throughout the length of New Zealand from the coast to as much as 1,

400 metres above sea level.

However,

All species have now undergone massive declines and populations nationwide are fragmented in few.

Four species,

Elegans,

Greyeye,

Flavoryctus,

And Punctatus are found only in the North Island.

What was previously thought to be a distinct population of Greyeye,

Found only in the far north on the Aopori Peninsula,

Has been determined from genetic work in the early 2000s to be a new species,

More closely related in fact to Elegans.

It was described as N.

Flavoryctus in 2021.

The remaining five species,

Gemmius,

Manikinus,

Ruddus,

Stellatus,

And Tuberculatus are found only in the South Island.

South Island Naldinus were in the past placed in a separate genus called Heterophallus,

But this taxon was abandoned when new genetic research in the 1980s showed little phylogenetic basis for this taxonomic division.

None of the Naldinus gecko populations are sympatric,

Presumably because each species is very finely adapted to its local environment and also because their respective ecological niches are incredibly similar.

Most of the world's 2,

000-odd species of geckos are active by night,

Nocturnal,

Whereas all species of Naldinus are active by day,

Diurnal.

Unlike their close relatives in the genus Hoplodactylus,

Naldinus species lack the ability to alter their skin color.

These geckos are omnivores.

Diet for members of this genus consists of flying insects,

Such as moths and flies,

But also of flightless invertebrates,

Such as amphipods and spiders.

All New Zealand geckos will supplement their primarily insectivorous diet and consume nectar and berries,

The small purple fruits of mahoi,

For example,

And there is evidence that in doing so,

They may have a function in New Zealand ecosystems as pollinators and seed dispersers for certain species of native plant.

In captivity,

They will thrive on a simple diet of moths and flies caught in traps.

New Zealand geckos have very few natural predators,

Although several species of native bird will take them as prey,

Only the sacred kingfisher kills very many.

The tuatara,

A large,

Ground-dwelling generalist predator,

Will feed on native geckos,

Including Naldinus,

Where the two occur together on a few predator-free offshore islands.

As ectotherms,

Naldinus geckos will move to positions of higher or lower temperature in order to thermoregulate.

Because Naldinus spend most of their time on the top of plant foliage,

They gain much of their heat directly from the sun.

Thus,

Control of the upper limits of temperature is achieved by moving from the outside of the foliage,

In areas of direct sunlight,

To shaded areas beneath the outside of the vegetation.

Control of the lower limits of temperature involves more movements for the animals.

Because New Zealand has a temperate climate,

Naldinus geckos live in areas which are at times,

Particularly in winter,

Exposed to very cold temperatures and high levels of rainfall.

In such adverse weather,

Animals will descend from an arboreal position in vegetation and seek shelter on the ground in and around the base of these same plants,

Or under rocks and other debris,

Where they are insulated to some degree against the cold air of the atmosphere.

Because external temperatures essentially dictate rates of metabolism in ectotherms,

The amount of food that these geckos will consume varies depending on the temperature and weather.

They will feed frequently in spring and summer,

And much less in the colder seasons of autumn and winter.

The four species of North Island Naldinus exhibit,

To varying degrees,

Defensive behaviors which involve gaping to reveal the vivid coloration of the interior of their mouths,

Bright red and flavorictus,

And deep blue and grey-eye,

Elegans and punctatus,

And in some cases,

Aggressive lunges and a strange sort of vocalization,

Which has been described as a barking sound.

These behaviors are an adaptation to startle and scare off potential predators,

And so to prevent the lizards from being eaten,

And have even been observed by people working against quite large mammalian predators,

Such as the domestic cat.

All four North Island Naldinus species will exhibit gaping behavior when threatened,

But in addition to grey-eye and punctatus,

Will lunge aggressively at the potential predator in question,

Often barking as they do so.

One source suggests that this pugnacious behavior is more a function of protection for an adult's young,

As they are only said to exhibit this behavior in the presence of juveniles,

The source saying that,

By contrast,

In the absence of young individuals,

They are usually very docile and easy to handle.

Like all New Zealand lizards,

Naldinus species will shed their tails to escape from predators,

But because they are prehensile and used for grasping as they climb,

They are much more reluctant to shed them than their close relatives in genus Hoplodactylus.

While most species of geckos in other parts of the world live for just a few years,

Naldinus are very long-lived in comparison.

They have been known to live for 30 years or more.

All New Zealand geckos,

And indeed all New Zealand lizards,

Except one species of skink,

Are viviparous,

Which is in contrast to most of the world's geckos,

Which are oviparous.

Females will actively move from areas of higher or lower temperature to thermoregulate,

In order to provide optimal temperatures for the development of their young inside them.

The young of all species are born a rich,

Velvety green,

Often with a series of markings on either side of the spine,

Which can be white,

Yellow,

Or tan.

Accoloration changes to the normal pattern and color of the adult at 15 to 18 months,

Around the time that young animals move out of their parental territories to set up territories of their own.

One explanation postulated for this is that the function is recognition of juveniles by adults.

It ensures that there is no danger of very young males being attacked or driven away from the family group by territorial-minded adult males.

Gestation period in New Zealand geckos is variable,

But observations of animals in captivity suggest that it is usually a relatively long process,

Usually around 8 to 9 months,

Similar to that of humans.

Reptiles in New Zealand were well known to Maori in pre-European times,

And featured in many carvings,

Some of which obviously depict tuatara and others which depict lizards.

The body shape of many examples suggests that they are geckos,

Though skinks also seem to be depicted.

With the exception of the tuatara,

Which was frequently eaten,

Lizards were regarded with aberrance by Maori,

And Naltanus in particular.

Sightings of Naltanus were regarded as bad omens.

Naltanus can legally be kept in captivity as pets in New Zealand,

Provided one has an appropriate permit from DOC and hundreds are kept in private collections all over the country.

Elegans,

Grey-eye,

And punctatas can all be kept on an A permit,

Which is the entry-level license given to new keepers,

While the remaining species in the genus require a B permit,

For which several years' experience keeping geckos is required.

In the past,

Animals could be collected from the wild to add to captive collections,

And this is how people typically used to enter the hobby.

This changed in 1981 when all species of native gecko were granted legal protection,

With the exception of two species of hoplodactylus,

The forest gecko and common gecko.

These two species were later also granted full protection in 1996.

These days,

Keepers must obtain their founder stock from an existing licensed breeder,

And animals can only be given away or swapped.

Sale of any sort of native lizard commercially is illegal.

A condition for granting an A permit is an inspection by DOC to ensure adequate quality of caging is provided,

And detailed records of changes in a collection must be kept.

Recording births,

Deaths,

Escapes,

And animals exchanged,

Received,

Or given away,

In annual forms submitted to DOC,

Are all legal requirement of the permit.

Many Naltinus keepers are members of the New Zealand Herpetological Society,

Which acts as a community hub for New Zealand herpetoculturalists.

Naltinus in private collections are often selectively bred for certain colors and patterns of coloration.

DOC has in recent years begun sourcing Naltinus,

Particularly punctatus,

For reintroduction to predator-free offshore islands from private collections,

On the condition that the animals are in good health and of pure genetic origin,

I.

E.

They haven't hybridized with other species.

Naltinus are also kept in captivity by enthusiasts in overseas countries,

But it should be stressed that trade is incredibly difficult,

And one must obtain adequate sites permits for importation and exportation.

This process is regulated by the site's management authority,

Which ascertains whether or not founding stock were obtained by a keeper in a particular country prior to 1981.

This is often quite difficult,

And usually prohibitive of international trade between Europe,

Where most stock resides outside of New Zealand and other countries.

Geckos are small,

Mostly carnivorous lizards that have a wide distribution found on every continent except Antarctica.

Belonging to the infra-order Geckoda,

Geckos are found in warm climates throughout the world.

They range from 1.

6 to 60 cm.

Geckos are unique among lizards for their vocalizations,

Which differ from species to species.

Most geckos in the family Geckonidae use chirping or clicking sounds in their social interactions.

They are the most species-rich group of lizards,

With about 1,

500 different species worldwide.

All geckos,

Except species in the family Eubliferidae,

Lack eyelids.

Instead,

The outer surface of the eyeball has a transparent membrane,

The brill.

They have a fixed lens within each iris that enlarges in darkness to let in more light.

Since they cannot blink,

Species without eyelids generally lick their own brills when they need to clear them of dust and dirt,

In order to keep them clean and moist.

Unlike most lizards,

Geckos are usually nocturnal and have excellent night vision.

Their color vision in low light is 350 times more sensitive than human eyes.

The nocturnal geckos evolved from diurnal species,

Which had lost the rod cells from their eyes.

The gecko eye therefore modified its cone cells that increased in size into different types,

Both single and double.

Three different photopigments have been retained and are sensitive to ultraviolet,

Blue,

And green.

They also use a multifocal optical system that allows them to generate a sharp image for at least two different depths.

While most gecko species are nocturnal,

Some species are diurnal and active during the day,

Which have evolved multiple times independently.

Many species are well known for their specialized toe pads,

Which enable them to grab and climb onto smooth and vertical surfaces and even cross indoor ceilings with ease.

Geckos are well known to people who live in warm regions of the world,

Where several species make their home inside human habitations.

These,

For example,

The house gecko,

Become part of the indoor menagerie and are often welcomed,

As they feed on insect pests,

Including moths and mosquitoes.

Like most lizards,

Geckos can lose their tails in defense,

A process called autotomy.

The predator may attack the wriggling tail,

Allowing the gecko to escape.

The largest species,

Giacarcanum del Corti,

Is only known from a single stuffed specimen,

Probably collected in the 19th century,

Found in the basement of the Natural History Museum of Marseille in Marseille,

France.

This gecko was 600 mm long,

And it was likely endemic to New Caledonia,

Where it lived in native forests.

The smallest gecko,

The Jaragua sphero,

Is a mere 16 mm long,

And was discovered in 2001 on a small island off the coast of Hispaniola.

The Neo-Latin gecko,

Spelled G-E-K-K-O,

And English gecko,

Spelled G-E-C-K-O,

Stem from Indonesian-Malaysian gekuk,

G-E-K-O-Q,

A Malay word borrowed from Javanese,

From tokek,

Which imitates the sound that some species like toke gecko make.

Like other reptiles,

Geckos are ectothermic,

Producing very little metabolic heat.

Essentially,

A gecko's body temperature is dependent on its environment.

Also,

To accomplish their main functions,

Such as locomotion,

Feeding,

Reproduction,

Etc.

,

Geckos must have a relatively elevated temperature.

All geckos shed their skin at fairly regular intervals,

With species differing in timing and method.

Leopard geckos shed at about 2-4 week intervals.

The presence of moisture aids in the shedding.

For young geckos,

Shedding occurs more frequently,

Once a week,

But when they are fully grown,

They shed once every 1-2 months.

About 60% of gecko species have adhesive toe pads,

Which allow them to adhere to most surfaces without the use of liquids or surface tension.

Such pads have been gained and lost repeatedly over the course of gecko evolution.

Adhesive toe pads evolved independently in about 11 different gecko lineages,

And were lost in at least 9 lineages.

It was previously thought that the spatula-shaped seedy arranged lamellae on gecko foot pads enable attractive Van der Waals forces,

The weakest of the weak chemical forces,

Between the b-keratin lamellae,

Seedy,

Spatula-y structures and the surface.

These Van der Waals interactions involve no fluids.

In theory,

A boot made of synthetic seedy would adhere as easily to the surface of the International Space Station as it would to a living room wall,

Although adhesion varies with humidity.

However,

A 2014 study suggests that gecko adhesion is in fact mainly determined by electrostatic interaction,

Caused by contact electrification,

Not Van der Waals or capillary forces.

The seedy on the feet of geckos are also self-cleaning,

And usually remove any clogging dirt within a few steps.

PTFE,

Which has very low surface energy,

Is more difficult for geckos to adhere to than many other surfaces.

Gecko adhesion is typically improved by higher humidity,

Even on hydrophobic surfaces,

Yet is reduced under conditions of complete immersion in water.

The role of water in that system is under discussion,

Yet recent experiments agree that the presence of molecular water layers,

Water molecules carry a very large dipole moment,

On the seedy,

As well as on the surface,

Increase the surface energy of both.

Therefore,

The energy gain in getting these surfaces in contact is enlarged,

Which results in an increased gecko adhesion force.

Moreover,

The elastic properties of the B keratin change with water uptake.

Gecko toes seem to be double-jointed,

But this is a misnomer,

And is properly called digital hyperextension.

Gecko toes can hyperextend in the opposite direction from human fingers and toes.

This allows them to overcome the Van der Waals force by peeling their toes off surfaces from the tips inward.

In essence,

By this peeling action,

The gecko separates spatula by spatula from the surface,

So for each spatula separation,

Only some force necessary.

The process is similar to removing scotch tape from a surface.

Gecko's toes operate well below their full attractive capabilities most of the time,

Because the margin for error is great depending upon the surface roughness,

And therefore the number of seedy in contact with that surface.

Use of small Van der Waals force requires very large surface areas.

Every square millimeter of a gecko's foot pad contains 14,

000 hair-like seedy.

Each seedy is in turn tipped with between 100 and 1,

000 spatulae.

The seedy of a typical mature 70 gram gecko would be capable of supporting a weight of 133 kilograms.

The exact value of the adhesion force of a spatula varies with the surface energy of the substrate to which it adheres.

Recent studies have moreover shown that the component of the surface energy derived from long-range forces,

Such as Van der Waals forces,

Depends on the material's structure below the outermost atomic layers.

Taking that into account,

The adhesive strength can be inferred.