Bad at Goodbyes

Rough Transcript

Intro 00:05

Welcome to Bad at Goodbyes.

On today’s show we consider the Montseny Brook Newt.

Species Information 02:05

The Montseny Brook Newt is a critically endangered amphibian native to the cold-water streams of the Montseny mountain in Catalonia in north-eastern Spain. Its scientific name is Calotriton arnoldi and it was first described in 2008.

 

Description

The Montseny Brook Newt is a small water-dwelling amphibian in the salamander family who measures roughly four inches in length, snout to tail-tip. They have a fairly long tail relative to their body, about one and a half inches of tail, to two and a half inches of body. Their body form is kind of flattened, they’re long, skinny, and low-profile, with four sturdy limbs. Their forelimbs have four unwebbed fingers, their hindlimbs have five unwebbed toes. Each toe has a hardened keratin tip, like a tiny claw.

 

Their head is wedge-shaped with two wide-set dark eyes, a blunt snout, with two wide-set nostrils.

 

Their skin is rough with tiny raised bumps, with a medium-brown to very dark-brown coloration on their back (that’s the dorsal side, the upper side) and a paler, creamier yellowish-tan on their neck and bellies (that’s the underside, the ventral side).

 

The Montseny Brook Newt does not have lungs. Instead, they rely on cutaneous and buccopharyngeal respiration. So cutaneous respiration: that’s skin. Our newt breathe via passive diffusion, a gas exchange between the oxygen-rich water of their mountain stream habitat, and tiny blood vessels (microcapillaries) pressed right against the very thin outer layer of their skin.

 

So Fick’s First Law of Diffusion, simplified, is that gas molecules tend to spread from areas of high concentration to areas of low concentration until they reach equilibrium. Until the concentration is the same throughout. So there’s a high concentration of dissolved oxygen in the river water. Our newt is constantly circulating and using the oxygen in its bloodstream to power its metabolism, so there’s a lower concentration there. And so in that imbalance, the water-oxygen diffuses through the outer layer of skin into the newt’s blood vessels, which circulate this now high oxygen concentrated blood deeper into the body, this circulation means that these outer skin microcapillaries are always lower concentrated, than the water, never at equilibrium. Resulting in a constant passive flow of oxygen into the newt’s bloodstream.

 

It works the same way for what we’ll just call their exhale. Stream water contains very little dissolved carbon dioxide, so the carbon dioxide in the newt’s blood diffuses out into the stream, washed away by the current, this current which similarly ensures there is never carbon dioxide equilibrium, the CO2 is always going out.

 

So that’s cutaneous respiration. The Montseny Brook Newt supplements its cutaneous respiration with buccopharyngeal respiration. Buccopharyngeal means mouth and throat. So if not enough oxygen is diffusing through the skin, the newt repeatedly takes in and expels gulps of water which come into contact with a microcapillary dense membrane in its mouth and throat to diffuse additional oxygen.

 

There’s another phenomenon at play here, too. No lungs means no internal air sacs. So the newt sinks. It has negative buoyancy. Imagine a balloon underwater, the lighter air quickly lifts the balloon to the water’s surface. But our newt does not have lungs, does not have balloon-like air sacs inside, so instead of rising through the water and getting pushed downstream by the current, it sinks, stable on the riverbed floor.

 

All of this is reliant upon and adapted to particularities of their habitat. Montseny Brook Newt live in flowing, high elevation, freshwater streams. This is cold turbulent water. Cold water can hold substantially more dissolved gas than warm water, so there is ample oxygen. And the turbulence is important as it provides a continuous new supply of oxygenated water and constantly pushes the carbon dioxide produced by the newt away. So like in still water, cutaneous respiration would quickly deplete the nearby oxygen adjacent to the skin, and carbon dioxide would build up to equilibrium, essentially suffocating the newt.

 

Behavior and Diet

Though this also means that unlike many amphibian species, the Montseny Brook Newt, is waterbound their entire lives, they cannot breathe air and hence cannot survive on land.

 

So, they spend their days resting in protective crevasses, their flattened body tucked under rocks or in thin cracks in the stony streambeds. They are nocturnal, active at night, they emerge after sunset to crawl the rocky river floor to feed.

 

The Montseny Brook Newt, is carnivorous both opportunistic and predatory. So they will forage for and feed upon the eggs and larvae of True Flies, Caddisflies, and Mayflies, that the current carries to the bottom of the riverbed. They’ll also, if the opportunity safely presents itself, consume the larvae of fire salamander, whose habitat overlaps with theirs.

 

And they will actively hunt small aquatic worms, crustaceans and snails. In the dark night waters exploring the crevasses, gravels, and leaf litter of the streambed, not by so much by sight, instead guided by olfaction (scent) and pheromones (detecting chemical signals in the water), and via mechanoreceptors that can detect vibrations indicating a crawling invertebrate. Finding prey the newt rapidly thrusts forward, seizing that prey with its teeth.

 

Reproduction

The Montseny Brook Newt is solitary. They tend to spread across their habitat, avoiding competition for resources and mainly only in contact with one another when mating. Montseny Brook Newt mate in the Spring and the Autumn. And the female will mate with multiple different males across a breeding season. 

 

Montseny Brook Newt mating is complicated by the flowing currents of their habitat. And so a male wraps a female with its tail, grasping her body for several hours, in an embrace that aligns their reproductive openings, their cloaca. In this position, the male releases a spermatophore (a protected sperm package) directly into the female’s cloaca (an opening used for waste excretion, reproductive intake, and egg-laying). And the female quickly uptakes the spermaphore before it’s washed away, to fertilize her eggs.

 

Following fertilization, the female deposits a clutch of 20-40 egg, one by one. Expelling each egg in rock fissures or beneath stones on the streambed to protect them from the current and from predators.

 

The eggs incubate for 1 to 2 months, and the new young hatch as tiny white-ish larvae with smooth skin and feathery external gills.

 

The lifecycle of the Montseny Brook Newt has four phases. So first, that two month egg phase. Then hatching and a gill-bearing larval phase that has been observed lasting three to six months in captivity though may be as long as eight to fourteen months in the wild. During this stage, their limbs begin to develop and they quadruple in size. The larva then retreats into deep fissures in the streambed for  metamorphosis. The newt larva absorbs its external gills and permanently closes its internal gill slits. Their skin undergoes rapid specialization, developing the microcapillaries it uses for breathing, and protective bumps and ridges and adopting a darkened adult coloration. This juvenile is essentially a smaller version of our adult. The juvenile phase lasts three-four years as the newt develops into reproductive maturity. Mature adults live for another roughly 5 years. A total lifespan of about 9 years.

In The Dream

————

In the dream,

 

A mountain stream.

The complex flow of water swirling and churning,

And the flow and swirl and churn of all life within it.

How all things move in a choreography of being.

 

The leaf on the current, the rush through the rapids,

The sediment shifting, the Turtle-Dove drinking, 

The young larvae changing, the newt in the fissure,

Or on the streambed embracing

 

The interrelation, the vital mechanics,

A mountain, a stream,

And the rippling, coursing ballet of living.

 

In the dream.

————

Habitat

The Montseny Brook Newt is native to Catalonia, in northeastern Spain, specifically to the El Montseny mountain massif, a series of peaks, part of the Catalan Pre-Coastal Range. The Montseny Brook Newt is found entirely within the El Montseny Natural Park and UNESCO Biosphere Reserve in a range spanning just 14 miles.

 

They live in fast-moving freshwater mountain streams at elevations ranging from roughly two thousand to four thousand feet. These are cool clear waters running over gravely fractured slate bedrock, through forests of oak, beech, alder, ash, and hazelnut, that provide moderate shade, and subsequent leaf litter to the riverbed.

 

We find the Montseny Brook Newt in two wholly divided subpopulations, cut through by the La Tordera River basin, a low-elevation valley that’s a barrier to subpopulation contact. Montseny Brook Newt show very high and compact site fidelity. A capture-tag study found that most adults only ranged on average, 8 feet, over the course of a year. And the few farther ranging adults averaged only 50 feet.

 

Summer highs in the region average in the low 70s°F; winter lows in the 30s°F, with roughly 35 inches of annual rainfall. 

 

The Montseny Brook Newt shares its streams and the surrounding forests with:

Stinking Hellebore, Common Bracken, Common Snowdrop, Woodland Dor Beetle, Eurasian Dotterel, Common Juniper, Dartford Warbler, Grey Long-eared Bat, European Holly, Poet’s Narcissus, Green-winged Orchid, Fire Salamander, Chapman’s Green Hairstreak, European Rabbit, Redwing, Red-legged Partridge, European Ash, Catalonian Wall Lizard, European Stag Beetle, Sweet Chestnut, Spiny Toad, Black-backed Meadow Ant, Common Hedgehog, Liverleaf, Marbled Newt, European Glow-Worm, Scotch Broom, Cirl Bunting, European Eel, European Beech, Common Redstart, European Turtle-Dove and many many more.

 

Threats

The Montseny Brook Newt population is currently threatened by anthropogenic (that is human-caused) habitat destruction and degradation. Historically, mining, logging, the transformation of forest into pastures, and the release of chemical pollutants have degraded the Montseny Brook Newt’s habitat in the Montseny peaks.

 

Today water over-extraction, waterway diversion, and agricultural use is reducing the amount of streamwater and affecting the speed of waterflow. Over the last roughly 25 years, the streamwaters of the Montseny range have been extracted for bottling and commercial sale, for agricultural wells and irrigation, for use at commercial tree farms, and diverted from their original watercourse via drainage pipes, artificial pools, and constructed channels.

 

As discussed, the Montseny Brook Newt requires very specific river conditions to survive and these habitat impacts have severely reduced their population. Our newt is considered the most threatened amphibian species in Europe.

 

Additionally, human-induced climate change, resulting from continued over-reliance on fossil fuels, exacerbates these problems. Warmer average global temperatures are resulting in longer dry seasons. Longer dry seasons means less streamwater and less streamflow. And over time, warmer air temp affects streamwater temperature as well, and warmer streamwater means less available oxygen for the Montseny Brook Newt.

 

Conservation

Fortunately the Montseny Brook Newt is legally protected at the local and international level, and their range is within the protected El Montseny Natural Park and UNESCO Biosphere Reserve.

 

An extensive conservation program was initiated in 2017, a collaboration between the Barcelona, Girona, Catalonia governments, with the Barcelona Zoo, Forestal Catalana, and the Biosphere Reserve.  Their work protected additional areas of the newt’s range, restored 7 streams’ original watercourses, built bridges over streamways reconnecting historical waterways, developed partnerships with local agriculture to reduce water-use, removed predatory invasive trout, and developed off-site captive breeding programs.

 

At the Torreferrussa Wildlife Center, the Barcelona Zoo, the Chester Zoo, the Pont de Suert Center, and the Calafell Research and Environmental Education Center, these breeding programs have developed processes to successfully breed the Montseny Brook Newt in captivity and have reintroduced more than 3000 individuals back into their natural habitat. Some of whom were microchipped for regular monitoring and tracking.

 

Nevertheless the Montseny Brook Newt has been considered critically endangered on the IUCN Red List since 2008 and their population is in decline.

 

Our most recent counts estimate that less than 1500 Montseny Brook Newt remain in the wild.

Citations 28:09

Information for today’s show about the Montseny Brook Newt was compiled from:

 

Amat, F., Oromí, N., Sanuy, D., & Carranza, S. (2015). Sexual dimorphism and age structure of the Montseny newt (Calotriton arnoldi). Amphibia-Reptilia, 36(3), 245-252. – https://doi.org/10.1163/15685381-00003000

 

AmphibiaWeb. 2026. University of California, Berkeley, CA, USA. – https://amphibiaweb.org/species/6666

 

Zoo de Barcelona. (n.d.). Conservation of the Montseny brook newt. – https://zoobarcelona.cat/en/conservation-of-the-montseny-brook-newt

 

Chester Zoo. (2026, July 21). Highly endangered newts hatched at Chester Zoo have been released at a secret site in Catalonia. – https://www.chesterzoo.org/news/highly-endangered-newts-hatched-at-chester-zoo-have-been-released-at-a-secret-site-in-catalonia

 

Contreras, J., Gomà, J., Velalcázar, D., & Montori, A. (2024). Thermal Tolerance and Preferred Temperature in the Critical Endangered Montseny Brook Newt (Calotriton arnoldi). Animals, 14(13), 1963. – https://doi.org/10.3390/ani14131963

 

García-Salmerón, A., Muñoz-Muñoz, F., Soler-Membrives, A., & Valbuena-Ureña, E. (2025). Head form variation in mountain newts of the genus Calotriton (Amphibia, Salamandridae) in a phylogeographic context. Zoologica Scripta, 54(4), 473–486. – https://doi.org/10.1111/zsc.12720

 

Guinart, D., Solórzano, S., Amat, F., Grau, J., Fernández-Guiberteau, D., & Montori, A. (2022). Habitat Management of the Endemic and Critical Endangered Montseny Brook Newt (Calotriton arnoldi). Land, 11(3), 449. – https://doi.org/10.3390/land11030449

 

iNaturalist – near Montseny, Spain

 

IUCN SSC Amphibian Specialist Group. 2022. Calotriton arnoldi. The IUCN Red List of Threatened Species 2022: e.T136131A89696462. – https://dx.doi.org/10.2305/IUCN.UK.2022-1.RLTS.T136131A89696462.en

 

Ledesma, J. L. J., Montori, A., Altava-Ortiz, V., Barrera-Escoda, A., Cunillera, J., & Àvila, A. (2019). Future hydrological constraints of the Montseny brook newt (Calotriton arnoldi) under changing climate and vegetation cover. Ecology and Evolution, 9(17), 9736–9747. – https://doi.org/10.1002/ece3.5506

 

Talavera, A., Palmada-Flores, M., Burriel-Carranza, B., Valbuena-Ureña, E., Mochales-Riaño, G., Adams, D. C., Tejero-Cicuéndez, H., Soler-Membrives, A., Amat, F., Guinart, D., Carbonell, F., Obon, E., Marquès-Bonet, T., & Carranza, S. (2024). Genomic insights into the Montseny brook newt (Calotriton arnoldi), a Critically Endangered glacial relict. iScience, 27(1), Article 108665. – https://doi.org/10.1016/j.isci.2023.108665

 

Talavera A, Valbuena-Ureña E, Burriel-Carranza B, Mochales-Riaño G, Adams DC, Amat F, Carbonell F, Carranza S. 2024. Integrative systematic revision of the Montseny brook newt (Calotriton arnoldi), with the description of a new subspecies. PeerJ 12:e17550. – https://doi.org/10.7717/peerj.17550

 

Tulloch, S., Estarellas, M., Adams, D. C., Bonacolta, A., Pagone, V., Fernández-Guiberteau, D., Amat, F., Montori, A., Carbonell, F., Obon, E., Alonso, M., Santmartín, M., Xarles, J., Marsol, R., Guinart, D., Solórzano, S., Talavera, A., Burriel-Carranza, B., Bosch, E., … Carranza, S. (2026). Comparative skin microbiome analyses reveal differences between wild populations and captive groups of the Montseny brook newt (Calotriton arnoldi). ISME Communications, 6(1), Article ycaf245. – https://doi.org/10.1093/ismeco/ycaf245

 

Valbuena-Ureña, E., Soler-Membrives, A., Steinfartz, S., Alonso, M., Carbonell, F., Larios-Martín, R., Obon, E., & Carranza, S. (2017). Getting off to a good start? Genetic evaluation of the ex situ conservation project of the critically endangered Montseny brook newt (Calotriton arnoldi). PeerJ, 5, Article e3447. – https://doi.org/10.7717/peerj.3447

 

Valbuena-Ureña, E., Soler-Membrives, A., Steinfartz, S., Obon, E., Amat, F., & Carranza, S. (2017). No signs of inbreeding despite long-term isolation and habitat fragmentation in the critically endangered Montseny brook newt (Calotriton arnoldi). Heredity, 118(5), 424–435. – https://doi.org/10.1038/hdy.2016.123

 

Wikipedia – https://en.wikipedia.org/wiki/Montseny_brook_newt

 

For more information about Montseny Brook Newt conservation, please see the Barcelona Zoo at https://zoobarcelona.cat/

Music 30:01

Pledge 38:13

I honor the lives of all Montseny Brook Newt. I will commit their name to my record. I am grateful to have shared time on our planet with this being. I lament the ways in which I and my species have harmed and diminished this species. I grieve.

 

And so, in the name of the Montseny Brook Newt I pledge to reduce my consumption. And my carbon footprint. And curb my wastefulness. I pledge to acknowledge and attempt to address the costs of my actions and inactions. And I pledge to resist the harm of plant and animal kin and their habitat, by individuals, corporations, and governments.

 

I forever pledge my song to the witness and memory of all life, to a broad celebration of biodiversity, and to the total liberation of all beings.