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Hula painted frog

The Hula painted frog (Latonia nigriventer) is a critically endangered amphibian species endemic to the marshes of the Hula Valley in northern Israel. It represents the sole surviving member of the genus Latonia within the family Alytidae.^[1] Characterized by its distinctive painted patterns of black spots and greenish hues on a yellowish background, the frog inhabits shallow aquatic environments with dense vegetation.^[2] Presumed extinct since the mid-20th century due to extensive habitat destruction from the drainage of Lake Hula for agricultural development and mosquito control, the species evaded detection for over 60 years until its rediscovery in 2011 within remnant marsh areas.^[2] This event highlighted its status as a "living fossil," with morphological and genetic analyses confirming its persistence as a relict lineage amid broader regional amphibian declines.^[2] Despite low population estimates, subsequent studies have revealed unexpectedly high genetic diversity and minimal inbreeding, suggesting some resilience in isolated subpopulations.^[3] Conservation efforts since rediscovery focus on habitat restoration in protected reserves, monitoring via environmental DNA techniques, and captive breeding to bolster numbers, though ongoing threats from water level fluctuations, invasive species, and climate variability persist.^[4] The frog's shy, primarily nocturnal behavior and limited vocalizations have historically contributed to underestimation of its distribution, underscoring challenges in assessing such cryptic species.^[5]

Taxonomy and Phylogeny

Classification and Nomenclature

The Hula painted frog, Latonia nigriventer, belongs to the family Alytidae within the order Anura.^[1]^[6] Its full taxonomic classification is as follows: Kingdom Animalia, phylum Chordata, class Amphibia, order Anura, family Alytidae, subfamily Discoglossinae, genus Latonia, species L. nigriventer.^[1]^[7] This species is the sole extant member of the genus Latonia, which otherwise comprises extinct taxa known from European fossil records dating to the Oligocene through Pleistocene epochs.^[2] Originally described in 1943 by Heinrich Mendelssohn and Heinrich Steinitz as Discoglossus nigriventer, the species was initially classified within the genus Discoglossus based on morphological similarities to other painted frogs.^[1]^[8] This synonymy persisted until phylogenetic analyses, prompted by the species' rediscovery in 2011, revealed deep genetic divergence from Discoglossus and alignment with the ancient genus Latonia (erected by Heinrich Rudolf Schinz in 1839 for fossil forms).^[2]^[8] The reclassification to Latonia nigriventer was formalized in 2013, emphasizing its status as a "living fossil" with morphological and molecular traits distinct from modern Alytidae congeners.^[2] Common names include Hula painted frog, reflecting its endemic occurrence in Israel's Hula Valley, and Palestinian painted frog, denoting the broader Levantine region historically associated with the type locality.^[1] No subspecies are recognized, given the limited population and genetic homogeneity observed post-rediscovery.^[2]

Evolutionary History as a Living Fossil

The Hula painted frog (Latonia nigriventer) is the only extant species in the genus Latonia, a lineage documented in the fossil record across Europe from the Oligocene to the Pleistocene.^[2] Molecular phylogenetic studies place L. nigriventer as the sister taxon to the clade comprising all extant Discoglossus species within the family Alytidae, with divergence estimated at approximately 32 million years ago (range: 19–70 million years ago), corresponding to the Late Eocene or Early Oligocene.^[2] This positions the genus as an ancient relict, predating the Miocene diversification of related painted frog lineages. Fossil evidence indicates that Latonia species, such as L. gigantea, were once widespread in European wetlands but abruptly vanished from the continental record during the Pleistocene, with the last occurrences in the Early Pleistocene (Calabrian stage).^[2] In contrast, Pleistocene fossils from sites in the Hula Valley, including Gesher Benot Ya'aqov (Early-Middle Pleistocene) and Nahal Mahanayeem Outlet (Late Pleistocene), exhibit osteological features identical to modern L. nigriventer, such as a double coronoid process and pterygoid flange—traits absent in Discoglossus.^[2] ^[9] These similarities demonstrate remarkable morphological stasis over at least 1–2 million years, supporting the classification of L. nigriventer as a living fossil that has persisted in isolated Levantine refugia while congeners went extinct elsewhere.^[2] The survival of Latonia in the Middle East, amid the genus's broader Eurasian decline, aligns with biogeographic patterns of amphibian relicta in marshy habitats resilient to climatic shifts.^[2] Osteological analyses using X-ray microtomography on extant and Hula Valley Pleistocene specimens further confirm functional morphology continuity, including robust cranial elements suited to the species' predatory lifestyle, with no significant evolutionary divergence from fossil ancestors.^[9] This persistence without substantial adaptation highlights L. nigriventer as a rare example of evolutionary conservatism in anurans, where genetic isolation and stable ecological niches preserved an ancient phenotype.^[2]

Physical Characteristics

Adult Morphology

The Hula painted frog (Latonia nigriventer) is a large, robust anuran species, with adult females exhibiting snout-vent lengths (SVL) ranging from 69.0 to 128.4 mm and males from 66.6 to 121.4 mm.^[1] ^[10] The body is broad, with width approximately twice that of the head, which is flattened and slightly wider than long.^[11] The snout is short and rounded, with an indistinct canthus rostralis; eyes are large, and the distinct tympanum measures about half the eye diameter.^[11] Dorsal coloration varies from ochre or yellowish-brown patches interspersed with rust-colored markings, grading into dark olive-grey or greyish-black tones, often featuring a light-colored vertebral stripe.^[1] The skin is granular, with raised tubercles more prominent in adults.^[10] Ventrally, the abdomen is characteristically black to dark grey, adorned with distinct white spots corresponding to wart-like tubercles, a diagnostic trait distinguishing it from congeners with lighter undersides.^[2] ^[1] Limbs are sturdy and relatively short; fingers lack webbing, while toes are partially webbed or free, adapted for terrestrial and aquatic movement in marshy habitats.^[11] A transversal dermal fold is present on the neck, contributing to the species' inconspicuous, camouflaged appearance despite its size.^[10] Color patterns show individual variation in contrast and distinctness but remain consistent across specimens, with post-metamorphic changes minimal in the ventral spotting.^[10]

Tadpole Morphology

The tadpoles of Latonia nigriventer exhibit a morphology broadly resembling that of its sister genus Discoglossus, with an elongated body adapted for aquatic life in shallow, vegetated waters. Total length ranges from approximately 14 mm at Gosner stage 24 to 24 mm at stage 34, with a maximum recorded length of 26 mm; body length at stage 34 measures about 8.9 mm.^[1]^[11] The body is elliptical in dorsal view and laterally depressed, with body width approximately 5.17 times body height; maximum width occurs at the anterior third (28.4% of body length), and maximum height between the second and third fifths (58% of body length), featuring a rounded snout. Eyes are medium-sized (8% of body length), dorsally positioned and laterally directed, located between the second and third tenths of body length (22% from snout to eye); interorbital distance equals 55% of body width. Nares are small (3% of body length), anteriorly oriented, positioned closer to the snout than to the eyes (35% of snout-nostril distance), with internarial distance at 45% of interorbital distance. The spiracle is crescentic, sinistral, and ventrally positioned with a medial opening, directed posteriorly at 56% of body length, and 4% of body length in size.^[11]^[1] The tail is moderately long (169% of body length), with maximum tail height at 89% of body height; dorsal and ventral fins reach 105% and 110% of tail muscle height, respectively, ending in an obtusely rounded tip, and the dorsal fin crest extends slightly onto the body dorsum while tail muscles terminate proximally. The oral disc is large (29% of body length), anteroventral in position, with labial tooth row formula (LTRF) 2/3(1), featuring 64 marginal papillae in a single row (with a break in the upper lip midline); the first anterior row spans 88% of oral disc width, and the gap in the third posterior row is 6% of that row's length. Lips bear a single row of papillae, interocular distance measures two-thirds of mouth length, and the mouth is wider than the interocular distance.^[11]^[1] In life, tadpoles display a medium brown dorsum with translucent quality, reticulated patterning, and golden speckles; fins are translucent with dark spots, and the ventrum and spiracle's ventral surface remain unpigmented. In preservative, the coloration darkens to granular dark brown with reticulated fins and a pale venter bearing grey spots. Nostril-snout distance is three-quarters the eye-nostril distance, spiracle width one-quarter mouth width, and the species features double keratodont rows, epidermal reticulations, and a medial ventral spiracle, distinguishing it from sympatric taxa such as Bufotes variabilis, Hyla savignyi, Pelophylax bedriagae, and Pelobates syriacus; relative to Discoglossus pictus, it has a shorter nostril-snout distance, wider mouth, and narrower spiracle.^[11]^[1]

Historical and Current Distribution

Original Habitat in Hula Valley

The Hula painted frog (Latonia nigriventer) was endemic to the freshwater wetlands of the Hula Valley in northern Israel, particularly the marshes and swamps encircling Lake Hula.^[2] This habitat encompassed approximately 59 km² prior to drainage, comprising Lake Hula (14 km² with a mean depth of 1.5 m) and surrounding swamps (32 km²), which expanded seasonally to 60 km² in winter due to flooding.^[12] The valley's subtropical climate featured short, wet, cold winters with 500–900 mm annual rainfall and long, dry, hot summers, sustaining a network fed primarily by the Jordan River, which split into deltaic branches entering the swamps.^[12] The environment consisted of shallow, lentic water bodies, including open swamps and densely vegetated areas dominated by Cyperus papyrus, Phragmites australis reeds, water ferns (Azolla filiculoides), and other aquatic plants that contributed to peat formation through degraded biomass.^[12] These wetlands hosted 11 distinct standing and running water habitats, supporting high biodiversity with 132 bird species, 16–19 fish species, and various amphibians.^[12] The frog occupied the eastern Hula Valley, favoring edges of permanent ditches with mud bottoms, slow-flowing water, dense aquatic vegetation (Phragmites, Pistia, Lemna), and adjacent terrestrial zones such as peaty soils, humid leaf litter, blackberry thickets, and reed stands.^[2]^[1]^[11] Historical records indicate the species was first collected in 1940 from these swampy locales, with subsequent observations in 1955 amid early drainage efforts, highlighting its reliance on undisturbed, organic-rich, colluvial-alluvial soils and wet detritus layers.^[2]^[1] The pre-drainage ecosystem's reduced geochemical conditions and persistent humidity provided ideal conditions for opportunistic breeding and nocturnal activity in both aquatic and terrestrial microhabitats.^[12]^[11]

Post-Drainage Persistence and Rediscovery Sites

Following the extensive drainage of Lake Hula and its marshes from 1951 to 1958, which eliminated approximately 95% of the original wetland habitat, the Hula painted frog (Latonia nigriventer) was believed to have gone extinct due to the loss of its aquatic and semi-aquatic breeding and foraging grounds.^[3] Small populations nonetheless persisted in remnant marshy refugia, particularly in undrained or partially preserved peat-rich areas that retained seasonal water and dense vegetation, allowing the species to survive through aestivation in moist soil during dry periods.^[2] These persistence sites were limited to fragments of the original Hula Valley ecosystem, including early conservation efforts that retained about 3% of the wetlands. The frog was rediscovered on November 15, 2011, when a single adult was observed by a ranger in a pond within the Hula Nature Reserve, a 3.5 km² protected area established in 1964 to safeguard remaining swamp remnants in northern Israel's Hula Valley.^[2] Subsequent surveys confirmed its presence at multiple locations inside the reserve, including marshes, reed beds, and ditches with permanent or semi-permanent water, as well as terrestrial microhabitats like leaf litter and grass tufts on damp peat soils.^[13] Further detections expanded known sites beyond the core reserve: two additional populations were identified approximately 1 km southeast near Yesod HaMa'ala village, in similar wetland fringes.^[13] Environmental DNA analysis has indicated potential occurrence at Agmon Ha-Hula Nature Park, a restored seasonal wetland adjacent to the reserve, and Ein Te'o Nature Reserve, though visual confirmations remain sparse in these areas.^[14] These sites represent the entirety of confirmed post-rediscovery distribution, confined to less than 10 km² of modified habitats vulnerable to ongoing agricultural pressures and water fluctuations.^[3]

Ecological Traits

Diet and Predation Dynamics

The Hula painted frog (Latonia nigriventer) exhibits carnivorous feeding habits, with limited direct observations due to its elusive, primarily nocturnal behavior. Analysis of gut contents from a preserved specimen revealed four land snails (Caracollina lenticula) and one isopod (Porcellionides cf. pruinosus), indicating a diet focused on hard-shelled terrestrial invertebrates.^[9] Its reinforced skull, enlarged adductor muscle insertion surfaces, and robust forelimbs support durophagous adaptations, facilitating the crushing of shelled prey that may be inaccessible to less specialized anurans.^[9] Historical records document cannibalism, as the holotype consumed a smaller conspecific frog in 1940, suggesting opportunistic predation on smaller vertebrates under certain conditions.^[9] Feeding in the wild has not been directly observed, but the species' semi-aquatic, ambush-oriented posture—often with only the rostrum exposed above water or substrate—implies sit-and-wait predation on mobile invertebrates encountered in peat-rich, vegetated microhabitats.^[11] Tadpoles likely consume algae, detritus, and small aquatic invertebrates, consistent with generalized anuran larval diets in wetland systems, though specific data for L. nigriventer remain unavailable. Predation dynamics exert significant pressure across life stages, contributing to observed low juvenile recruitment and population bottlenecks. Adults face threats primarily from avian predators, including white-throated kingfishers (Halcyon smyrnensis), which target the frog's robust form in shallow waters.^[1] Juveniles and tadpoles are vulnerable to a diverse array of aquatic and semi-aquatic predators, such as western mosquitofish (Gambusia affinis), dragonfly nymphs, freshwater crustaceans, Caspian turtles (Mauremys caspica), lycosid spiders, carabid beetles, and larger anurans including conspecifics and marsh frogs (Pelophylax bedriagae).^[11] Evidence of predation includes hind-limb injuries in 28% of medium- to large-sized adults captured at rediscovery sites, likely from failed escape attempts by birds or turtles grasping the limbs during submergence.^[11] The frog's cryptic coloration, burrowing tendencies, and preference for dense vegetation mitigate risks, but high densities of invasive fish and post-restoration waterbird populations in the Hula Valley amplify early-stage mortality, underscoring predation as a key limiter in its precarious trophic niche.^[1]^[11]

Reproductive Strategies

The Hula painted frog (Latonia nigriventer) employs an opportunistic reproductive strategy adapted to permanent aquatic habitats, with breeding inferred to occur without specialized parental care, akin to its relative Discoglossus. Mating involves inguinal amplexus, as deduced from phylogenetic position within Discoglossidae, though no direct observations exist post-rediscovery.^[11] The breeding period spans February to September, evidenced by nuptial pads on males active from mid-February to mid-September and adult presence in water bodies during this interval.^[11] ^[1] Egg deposition has not been directly witnessed, but dissection of a gravid female in mid-January revealed several hundred greyish-black oocytes measuring 1.5–2 mm in diameter, indicating clutches of comparable size laid in water.^[11] Tadpoles, observed historically in 1940 and post-2011 in sites like the Yesod HaMa’ala ditch, measure 14 mm total length at Gosner stage 25 and 24 mm at stage 34, featuring uniform brown dorsum, unpigmented venter, medial ventral spiracle, and labial tooth row formula 2/3(1).^[11] ^[15] Larval development proceeds aquatically, with metamorphosis documented from 3–15 June in captive-reared individuals originating from May collections; of 40 tadpoles raised, 9 survived to post-metamorphosis (snout-vent length 6–9 mm).^[11] Field surveys from 2013–2015 recorded 40 tadpoles among 137 total individuals (64 females, 42 males, 29 juveniles), alongside juveniles on land from November to March under humid litter, underscoring comparatively low recruitment and recruitment rates that may sustain populations through prolonged aquatic adult phases amid fluctuating conditions.^[11] ^[1] This strategy contrasts with more explosive breeding in seasonal pond species, prioritizing persistence in stable, albeit rare, wetland refugia over high-volume offspring production.^[11]

Vocalization Patterns

The Hula painted frog (Latonia nigriventer) produces vocalizations of low intensity, lacking the vocal sacs typical in many anuran males that amplify calls for long-distance advertisement.^[16] These calls are primarily uttered by adult males at the water surface, likely serving short-range communication functions such as mate attraction during breeding periods. Observations indicate calls are emitted in series, with inter-call intervals ranging from 246 to 1606 milliseconds, under ambient conditions of air temperatures 13.5–18 °C and water temperatures 14–15 °C.^[1]^[11] The presumed advertisement call consists of two spectral, pulsatile notes: an initial longer expiratory note followed by a shorter inspiratory note of lower frequency but higher intensity. Each call lasts 725–1212 milliseconds, with a dominant frequency of approximately 775 Hz (range 0–1500 Hz), rendering them challenging for humans to detect amid environmental noise in natural habitats.^[1]^[11] Both sexes generate release calls upon handling or disturbance, which closely resemble the advertisement calls in structure and sound. Recordings of these vocalizations, obtained from captive males in February 2015, confirm their subdued acoustic profile, analyzed via software like Cool Edit Pro and archived in databases such as FonoZoo.^[1]^[11] Field surveys post-2011 rediscovery have rarely documented vocal activity, attributable to the species' cryptic behavior and the low-amplitude emissions, which may prioritize energy conservation in a fragmented, predator-rich marsh environment over conspicuous broadcasting. No evidence supports ultrasonic components beyond human hearing, contrary to anecdotal claims; empirical acoustic analyses affirm audibility within low-frequency bands.^[1]^[11]

Population Dynamics and Decline

Pre-1950s Abundance

The Hula painted frog (Latonia nigriventer) was first documented in the Hula Valley on October 22, 1940, when researchers collected two adult specimens and two tadpoles from the eastern marshes.^[11] This initial discovery occurred within the expansive wetlands of the valley, which encompassed Lake Hula (approximately 12–14 km²) and surrounding swamps fluctuating seasonally between 21 km² and 60 km² in extent.^[17]^[18] The shallow, nutrient-rich waters and dense vegetation provided optimal conditions for amphibian life, supporting at least four frog species in the pre-drainage era.^[12] No quantitative population estimates exist for L. nigriventer prior to the 1950s, as surveys were limited and the species exhibited cryptic behaviors, including predominantly nocturnal activity, shy aquatic habits, and subdued vocalizations that hindered detection.^[11] The scarcity of additional records—none between 1940 and the post-war period—suggests either inherently low density or under-sampling in a habitat teeming with biodiversity, where other amphibians were more readily observed.^[2] The intact ecosystem, characterized by permanent and seasonal marshes, likely sustained viable populations adapted to the valley's hydrological regime.^[12]

Impact of Lake Hula Drainage

The drainage of Lake Hula and its surrounding marshes, spanning 1951 to 1958, eliminated approximately 95% of the original 44 km² wetland ecosystem, converting it into agricultural fields primarily to control malaria and expand farmland.^[19] This radical alteration destroyed the shallow, vegetated aquatic habitats critical for the Hula painted frog (Latonia nigriventer), which relied on seasonal flooding and permanent swamps for breeding, tadpole rearing, and adult refuge.^[2] The species, previously abundant across the Hula Valley's ~6.5 km² endemic range, experienced immediate population collapse as desiccation rendered former breeding sites arid and unsuitable for amphibian life cycles.^[3] Post-drainage surveys documented the frog's disappearance by the late 1950s, with no confirmed sightings thereafter until 2011, attributing the decline directly to habitat loss rather than secondary factors like disease or predation shifts.^[2] The transformation exacerbated vulnerability by fragmenting any residual microhabitats, such as ditches and canals, which proved insufficient to sustain viable populations amid intensified agricultural runoff and groundwater depletion.^[20] Broader ecological fallout included the regional extinction or extirpation of multiple amphibian-associated species, underscoring the drainage's role as a primary driver of biodiversity erosion in the valley.^[21] Quantitative assessments post-event revealed a stark reduction in wetland-dependent taxa, with the Hula painted frog symbolizing the drainage's irreversible impacts on specialized endemics adapted to the pre-alteration hydrology.^[12] Peat subsidence and soil salinization further degraded surviving fragments, compounding habitat unsuitability and preventing natural recolonization.^[22] Despite partial reflooding efforts in the 1990s restoring ~3 km², the initial drainage's scale ensured long-term demographic bottlenecks for the frog, as evidenced by low genetic diversity in rediscovered individuals.^[10]

Period of Presumed Extinction (1950s–2011)

Following the extensive drainage of Lake Hula and its marshes from 1951 to 1958, which eradicated approximately 95% of the species' wetland habitat to control malaria and enable agriculture, Latonia nigriventer sightings ceased almost entirely.^[23] The final verified record prior to the rediscovery was a solitary adult specimen captured in 1955 near the remnants of the Hula Valley wetlands.^[1]^[24] No subsequent confirmed observations occurred despite targeted surveys in the diminished aquatic refugia, fostering a consensus among herpetologists that the population had succumbed to habitat loss and associated ecological disruptions by the late 1950s.^[25] Periodic, unverified claims of potential encounters surfaced during this interval but lacked substantiation through specimens or photographic evidence. For instance, in 2000, a representative from the Lebanese conservation group A Rocha reported observing a frog resembling L. nigriventer in the Aammiq Wetland south of Lebanon's Beqaa Valley, yet follow-up investigations failed to confirm the identification.^[26] Israeli authorities, including the Society for the Protection of Nature, conducted repeated expeditions in the Hula Nature Reserve—established in 1964 on a fraction of the original marshland—but documented no traces of the frog amid ongoing monitoring for other amphibians and avifauna.^[27] By 1996, after more than four decades without validated detections, the International Union for Conservation of Nature (IUCN) classified Latonia nigriventer as extinct—the first amphibian to receive this designation—attributing the decline primarily to anthropogenic wetland conversion rather than disease or predation pressures prevalent in other amphibian extinctions.^[28]^[29] This status persisted unchallenged in scientific literature, underscoring the frog's role as an emblem of irreversible habitat-driven biodiversity loss in the Levant region, until anomalous findings in late 2011 prompted reassessment.^[2]

2011 Rediscovery and Subsequent Surveys

On 15 November 2011, a park ranger during a routine patrol in the Hula Nature Reserve discovered a single adult Latonia nigriventer specimen, marking the first confirmed sighting since 1955 and overturning its presumed extinction status.^[1] This individual was identified as an adult male through morphological examination, confirming its species via distinctive black spots and painted patterns absent in co-occurring amphibians.^[2] Following the initial discovery, intensive field surveys were initiated in the Hula Valley, focusing on restored wetlands and remnant marsh habitats within the reserve. Between 2011 and 2016, researchers captured a total of approximately 155 individuals, with 89% concentrated in a single pond, indicating highly localized distribution and microhabitat dependence.^[3] Genetic monitoring using microsatellite loci on 125 specimens revealed high genetic diversity and minimal inbreeding, suggesting a resilient core population despite historical bottlenecks.^[30] Subsequent efforts incorporated environmental DNA (eDNA) sampling in 2017 across suitable aquatic sites, detecting L. nigriventer DNA in 22 locations clustered within three primary areas of the reserve, expanding known occupancy beyond visual captures but confirming no extralimital populations.^[31] Population size estimates derived from capture-recapture and genetic models yielded adult abundances of 234–244 (Na) and effective sizes (Ne) of 16.6–35.8, underscoring vulnerability to stochastic events despite recruitment evidence from juveniles.^[20] Ongoing annual surveys through 2023 have documented sporadic breeding but persistent rarity, with no significant range expansion observed.^[10]

Conservation Assessment

IUCN Status and Population Estimates

The Hula painted frog (Latonia nigriventer) is classified as Critically Endangered on the IUCN Red List due to its extremely restricted extent of occurrence, estimated at less than 2 km², and persistent habitat degradation threats following drainage of Lake Hula in the 1950s.^[1]^[3] This status was updated after the species' rediscovery in 2011, reversing its prior declaration of Extinct in the Wild in 1996, though the population remains perilously small and fragmented across limited marsh remnants in Israel's Hula Valley.^[1] Population estimates derive primarily from capture-recapture and genetic surveys, indicating low abundance. A 2018 analysis using microsatellite markers estimated the census population size (N_c) of potentially breeding adults at 234–244 individuals, with an effective population size (N_e) of 16.6–35.8, suggesting sufficient genetic diversity to avoid immediate inbreeding depression despite historical bottlenecks.^[3] Field surveys from 2015 to 2017 documented 175 individuals across four sites, underscoring confinement to small, isolated subpopulations vulnerable to stochastic events.^[1] No comprehensive peer-reviewed population updates have been published since 2018, though ongoing monitoring in protected reserves continues; informal reports as of 2025 suggest totals may not exceed 400 individuals globally, but these lack quantitative validation.^[32] The IUCN criteria for Critically Endangered are met under B2ab(iii) (severely fragmented habitat with continuing decline) and potentially D (very small population), emphasizing the need for precise demographic tracking to inform recovery.^[1]^[3]

Primary Threats and Causal Factors

The drainage of Lake Hula and its surrounding marshes between 1953 and 1958, undertaken primarily for agricultural expansion and malaria vector control, constituted the principal causal factor in the drastic population decline of Latonia nigriventer, eliminating approximately 95% of its wetland habitat and fragmenting remaining aquatic refugia.^[23] This anthropogenic alteration directly disrupted breeding sites, foraging areas, and hydrological regimes essential for larval development, as the species depends on shallow, vegetated marshes for reproduction and survival.^[2] Post-drainage surveys documented the absence of the frog from former localities, attributing the collapse to habitat loss rather than stochastic events or disease, given the species' prior abundance in the unaltered ecosystem.^[1] Ongoing habitat degradation in the remnant Hula Valley reserve, where the sole known population persists within less than 2 km², represents the foremost contemporary threat, exacerbated by fluctuating water levels, invasive vegetation encroachment, and agricultural runoff.^[19]^[11] Although L. nigriventer demonstrates tolerance for moderately polluted and modified environments—surviving in a single artificial pond amid intensive land use—cumulative effects from eutrophication and altered hydroperiods continue to impair recruitment, as evidenced by low juvenile detection rates in surveys following the 2011 rediscovery.^[1] Predation pressure from introduced fish and avian species has intensified in this confined range, with concentrated frog densities facilitating higher per capita mortality; genetic analyses indicate inbreeding depression and reduced fitness, compounding vulnerability to these biotic interactions.^[3] While chytridiomycosis and other pathogens pose risks to amphibians globally, no confirmed outbreaks affect L. nigriventer, and its persistence amid severe habitat perturbation underscores habitat integrity as the dominant causal driver over infectious agents.^[2] Climate-induced shifts in precipitation could further stress wetland hydrology, but empirical data from the Hula Valley prioritize anthropogenic modification as the binding constraint on recovery, with IUCN assessments inferring continued decline absent habitat restoration.^[16]

Implemented Measures and Outcomes

Following the drainage of Lake Hula in the 1950s, which severely impacted the species' habitat, Israeli authorities initiated wetland restoration in the Hula Valley, including partial reflooding of marsh areas starting in the 1960s and the establishment of the Hula Nature Reserve in 1964. These efforts aimed to recreate suitable aquatic and vegetated environments by improving water quality and hydrology, reversing some effects of agricultural conversion and contributing to the frog's undetected persistence and eventual rediscovery in November 2011 within the reserve.^[33] Post-rediscovery, the Israel Nature and Parks Authority designated Latonia nigriventer as a protected species and launched monitoring protocols, including photographic recapture using unique dorsal and ventral markings to track individuals and estimate population parameters. Habitat management within the reserve focuses on maintaining shallow ponds and emergent vegetation, with recommendations for further restoration to enhance water flow and reduce invasive species, as genetic analyses indicate viable diversity but vulnerability to inbreeding if numbers remain low.^[19]^[3]^[11] In response to elevated threats from regional conflict, authorities conducted a relocation operation in November 2024, moving individuals from exposed sites in the Hula Reserve to more sheltered internal ponds to avert potential extinction from rocket or drone strikes. Outcomes include the confirmation of multiple breeding events post-2011, with environmental DNA surveys detecting presence across limited reserve patches, but population estimates remain critically low—fewer than 100 adults based on capture-recapture data—yielding no substantial increase despite interventions, as ongoing habitat fragmentation and predation pressures persist.^[34]^[20]^[3]

Debates on Extinction Risk and Recovery Potential

The Hula painted frog (Latonia nigriventer) is classified as Critically Endangered by the IUCN, with its extent of occurrence limited to less than 2 km² and ongoing threats from habitat alteration and invasive species. Population estimates indicate a small number of potentially reproducing adults, ranging from 236 to 244 individuals, alongside an effective population size (N_e) of 16.6–35.8, signaling heightened vulnerability to stochastic events and demographic fluctuations.^[3] Debates center on the interplay between this demographic precariousness and unexpectedly robust genetic health. While low N_e typically forecasts rapid genetic erosion and elevated extinction risk, genetic analyses reveal high diversity— with observed heterozygosity of 0.531–0.911 and low inbreeding coefficients (-0.103 to 0.069)—suggesting recent admixture or undetected subpopulations that buffer against immediate collapse.^[3] ^[35] Proponents of dire risk emphasize the species' localization to four restricted sites, opportunistic yet constrained breeding, and exposure to Batrachochytrium dendrobatidis (Bd) fungus, despite absence of clinical chytridiomycosis, as compounding factors in a fragmented habitat prone to hydrological changes.^[36] ^[37] Conversely, advocates for recovery potential highlight the frog's historical resilience—surviving presumed extinction from 1950s drainage undetected for decades—and traits like year-round aquatic residency and high polymorphism, which may enable adaptation if threats are mitigated through habitat corridors, restoration, and targeted interventions such as translocation or captive breeding.^[3] ^[36] This genetic vigor, atypical for such small populations, implies a window for proactive conservation to avert re-extinction, though empirical monitoring of recruitment and connectivity remains essential to resolve whether diversity translates to demographic rebound.^[35]

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https://doi.org/10.1111/mec.14398
[15]
Hula painted frog - Facts, Diet, Habitat & Pictures on Animalia.bio
### Reproductive Biology of Hula Painted Frog
[16]
Creature Feature: Hula Painted Frog - The Ethogram
Sep 19, 2023 · Meet the Hula painted frog (Latonia nigriventer), a small, colorful amphibian native to the Hula Valley in Israel, with a captivating history.
[17]
Hula Valley before the drainage 1949. Adapted ... - ResearchGate
The Hula Wetland was characterized with high species and habitat diversity, with 11 different standing and run- ning water habitats (Breslavsky 1955 ...Missing: pre- | Show results with:pre-
[18]
Geography of Israel: Hula Valley
Prior to its drainage in the 1950s, Lake Hula was 5.3 kilometres long and 4.4 kilometres wide, extending over 12-14 square kilometres. It was a shallow, pear- ...
[19]
Hula Painted Frog, Discoglossus nigriventer
It is a medium-sized frog with rush-colored patches on the back and a dark belly with white spots. The Hula Painted Frog occurs on the edge of freshwater ...Missing: larval stage
[20]
Population genetic analysis of the recently rediscovered Hula ...
Apr 3, 2018 · The Hula painted frog (Latonia nigriventer), endemic to a small (~6.5 km²), extensively modified region in northern Israel, gained notoriety by ...
[21]
[PDF] Lakes Hula and Agmon: destruction and creation of wetland ...
Before draining of the Hula, the Jordan River split again into three main deltaic branches be- fore entering the swamps.
[22]
Draining Israel's Hula Valley | Bar Ilan University
Oct 31, 2021 · The Hula Valley was drained to prepare agricultural land, which deteriorated the Sea of Galilee's water quality and caused the land to sink.
[23]
Extinct frog rediscovered in Israel - Mongabay
Not recorded since 1955, the Hula painted frog vanished after 95 percent of its wetland habitat was drained to fight malaria and grow crops. The draining also ...Missing: persistence | Show results with:persistence
[24]
Frog long thought extinct rediscovered in Israel - Science News
Jun 4, 2013 · When scientists first spotted the painted frog in the 1940s in Israel's Hula Valley, they classified it as Discoglossus nigriventer for its ...
[25]
First Amphibian Declared Extinct 'Rediscovered' in Israel's Hula Valley
Jun 5, 2013 · A Hula painted frog. surviving member of an extinct genus of frogs. First discovered in Israel's Hula Valley in the 1940s, the Hula painted frog ...
[26]
Hula painted frog - Facts, Diet, Habitat & Pictures on Animalia.bio
The Hula painted frog (Latonia nigriventer ) is an amphibian and the only ... It was thought to be extinct as a result of habitat destruction during the 1950s ...Missing: threats | Show results with:threats<|control11|><|separator|>
[27]
Long Thought Extinct, Hula Painted Frog Found Once Again in ...
Nov 17, 2011 · Long Thought Extinct, Hula Painted Frog Found Once Again in Israeli Nature Reserve. Rare find is akin to the Dead Sea Scrolls of nature ...
[28]
Reports of Frog's Extinction Have Been Greatly Exaggerated
Jun 4, 2013 · If the Hula painted frog—now Latonia nigriventer—had actually gone extinct in the 1950s, its entire genus would have disappeared too.
[29]
Rediscovered Hula painted frog 'is a living fossil' - BBC News
Jun 4, 2013 · The Hula painted frog was last seen in Israel the 1950s - until it was found again in 2011 by a park ranger ... extinct in 1996, the hula painted ...
[30]
Population genetic analysis of the recently rediscovered Hula ...
After its recent rediscovery, the Hula painted frog (Latonia nigriventer) has remained one of the world's rarest and least understood amphibian species.<|separator|>
[31]
Uncovering the current distribution pattern of the rediscovered Hula ...
Nov 12, 2017 · Since its rediscovery in 2011, individuals from the critically endangered species have been found, with great effort, only in four restricted ...<|separator|>
[32]
Hula Painted Frog! - Yoav Perlman
Mar 9, 2025 · Since then, it was found only in a handful of sites in the Hula Valley, with an estimated global population of not more than 400 individuals! I ...Missing: persistence | Show results with:persistence
[33]
Hula painted frog - Wikipedia
The Hula painted frog (Latonia nigriventer) is a species of frog endemic to the Lake Hula marshes in northern Israel. It is the only living member of the ...Taxonomy · Distribution and habitat · Biology · StatusMissing: threats | Show results with:threats
[34]
Watershed moment for extinct Israeli frog - ISRAEL21c
Jan 3, 2012 · The Hula painted frog was considered a relic of history, until a vigilant park warden spotted the creature jumping back into existence.Missing: nomenclature | Show results with:nomenclature
[35]
Conservationists rush to save species from war - Ynetnews
Nov 13, 2024 · Nature reserve launches operation to remove Hula painted frog from rocket, drone attacks that could wipeout entire population, relocating them ...Missing: actions | Show results with:actions
[36]
Evolutionary principles guiding amphibian conservation - PMC
That said, conservation strategies employing evolutionary principles, such as selective breeding ... (Latonia nigriventer) reveals high genetic diversity and low ...
[37]
Natural history and conservation of the rediscovered Hula painted ...
The enigmatic Hula painted frog (Latonia nigriventer), the first amphibian to be declared extinct but unexpectedly rediscovered in 2011, has remained one of the ...
[38]
[PDF] Uncovering the current distribution pattern of the rediscovered Hula ...
It was first described as Discoglossus nigriventer following the discovery of two specimens on the east shore of the Hula Lake in northern Israel in 1940 ( ...