Feliz cumpleaños, 21 years for the Beni Anaconda, Eunectes beniensis (Dirksen, 2002) (Serpentes, Boidae): an update of voucher specimens, species’ distribution, and clarification of locality data of type specimens

. Little information for Eunectes beniensis (Dirksen, 2002) (Serpentes, Boidae) exists in the scientific literature and museum data. We review the natural history, diet, reproduction, distribution of this species and discuss its identifying characteristics. We present new records and discuss the species’ distribution in Bolivia. As reported in the previous literature, the geographic locality data of the holotype and paratypes are incorrect. We report corrected data for these specimens and update knowledge of the species’ distributional status and natural history by summarizing novel and existing data from the entirety of this species’ known range. We provide a distribution map based on vouchered museum specimens.


Introduction
The genus Eunectes Wagler, 1830 is a group of large, semiaquatic, booid snakes (Serpentes, Boidae) composed of four species, whose combined range extends from northern South America to Argentina (Henderson et al. 1995;Wallach et al. 2014;Reynolds et al. 2018).Eunectes beniensis (Dirksen, 2002), E. murinus (Linnaeus, 1758), and E. notaeus (Cope, 1862) are all known to occur in Bolivia (Dirksen 2002;Wallach et al. 2014;Reynolds et al. 2018;Uetz et al. 2022).Eunectes murinus (Green Anaconda) was described over two centuries ago and has been considered a single species broadly distributed throughout many South American biomes (Peters and Orejas-Miranda 1970;Henderson et al. 1995;McDiarmid et al. 1999;Nogueira et al. 2019).Eunectes notaeus (Yellow Anaconda) occurs in the Paraguay river drainage, from the Pantanal Region in southeastern Bolivia, Paraguay, and Brazil, to northeastern Argentina (Henderson et al. 1995;Dirksen 2002;Waller et al. 2007;Kershaw et al. 2013).During a revision of the genus, E. beniensis was separated from E. murinus and E. notaeus as a new, distinct species based on ventral and dorsal scale counts, contact between suboculars and supralabials, head stripe pattern, pattern of body marking, and coloration (Dirksen 2002;Dirksen and Böhme 2005).Recently, Tarkhnishvili et al. (2022) completed a molecular analysis of the genus Eunectes that supported two distinct evolutionary lineages; one lineage consists of only E. murinus and is genetically divergent from the other group containing three species (E. deschauenseei, E. beniensis, and E. notaeus), which are all more closely related incipient species (but morphologically distinct) putatively maintained by geographic isolation.
There are limited information and data regarding the natural history, diet, and reproduction of E. beniensis (i.e. as compared to other species of Eunectes).Dirksen and Böhme (2005) and Embert (2009) acknowledged the overall lack of information but commented that E. beniensis will probably be generally similar to other species of Eunectes.Dirksen and Böhme (2005) commented on the diurnal activity and protective balling-posture behavior.Embert (2009) listed habitat as Beni flooded savannas and parts of southern Amazonia.Additionally, Embert (2009) also commented on the probability of reproductive activity (i.e.September-October with birth in April-May) but failed to provide any supportive data.De la Quintana et al. (2017) used radio telemetry to study home range and habitat use of nine radiotagged individuals and reported the species' preference for flooded savannas and swamps and apparent avoidance of forest and agricultural areas (i.e.rice fields).In a recent comprehensive literature review comparing documented prey of Eunectes species, Thomas and Allain (2021) listed only one citation for E. beniensis (De la Quintana et al. 2011), reporting a case of cannibalism.This overall lack of information on E. beniensis is possibly, in part, due to the species' historical inclusion and confusion with E. murinus.In addition, relatively few specimens have been collected from Bolivia and deposited in museums as voucher materials; this could be due partially to the species' large adult size and difficulties associated with capture, transport, and preservation of specimens.For example, in some cases only the head or the skin with head and tail was preserved.
The geographic distribution and natural history of E. beniensis has been poorly documented and studied since its original description in 2002.Therefore, to improve knowledge of this species, our objectives are to: 1) describe several new voucher specimens of E. beniensis collected from Bolivia in the departments of Beni and Santa Cruz, 2) present a list of specimens that we were able to locate and verify in museum collections, 3) report on numerous errors in the geographic locality data of the holotype and paratypes of E. beniensis and correct these data, 4) discuss identifying characteristics not previously reported for E. beniensis, and 5) present and discuss the species' distribution based on the results of the aforementioned objectives.

Methods
Scale counts, scutellation, and terminology follow Dowling (1951) and Peters (1964).Head-scale counts (i.e.loreal, preocular, postocular, supralabials, infralabials, and temporal) were reported on one side only.Dorsal scale row counts were taken at three standardized locations: head length behind occiput, midbody, and head length anterior to cloaca; these are separated by a slash (/).Measurements were taken using a flexible ruler to the nearest millimeter.Weight of the specimens in kilograms (kg) was determined using a CK model (12.5 kg) spring balance.Sex was determined by the probe method following McDiarmid et al. (2012) and confirmed by injection following Simmons (2002).Specimen identification was determined by comparing and analyzing meristic data, morphometrics, coloration, figures, photographs, and descriptions following Dirksen (2002) and Dirksen and Böhme (2005) for Eunectes beniensis.Specimens were fixed with a 10% formalin solution and preserved in a 70% ethanol solution.Geographic coordinates in decimal degrees (rounded to four decimal places) were determined using a Garmin etrex GPS receiver using the WGS84 datum.For specimens where coordinates were estimated from a map using a general locality name, decimal degrees were limited to three decimal places.Specimens are associated with specific coordinates where data permit (unless otherwise noted).The record and distribution map were prepared using ArcMap v. 10.1 (ArcGIS software).
For records published with only a textual description of the location, we determined the latitude and longitude coordinates using Google Earth.We defined coordinates based on the approximate center of the named locations for these specimens with the centroid coordinates 0.5 km in relation to the perimeter.
The newly collected specimens were deposited in the herpetology collection of the Centro de Investigación de Recursos Acuáticos in Trinidad, Beni, Bolivia.Research was approved by the Texas A&M University-Kingsville (#2018-05-22) Animal Care and Use Committee and permitted by the Dirección General de Biodiversidad y Áreas Protegidas Bolivia (permit #0120/2022).
Color, pattern, and description: stout-bodied with head large and slightly differentiated from neck.Dorsum ground color olive-brown with 87-126 large, dorsal, black blotches, separated by three or four scales with smaller, solid, roundish or irregularly shaped, black blotches throughout flank region.Head color same as dorsum, with five distinct, black, longitudinal stripes, two or three scales wide (Fig. 3), one median dorsal, one pair of dorsolateral, and one pair of lateral stripes; lateral stripe starting from posterior eye to slightly past mouth.Eyes medium-sized, slightly dorsal, with elliptical pupil and brown to bronze iris.Ventral color yellow, with numerous black irregular marks throughout and sometimes forming interrupted longitudinal shapes.

Discussion
Past literature has reported erroneous geographic locality data for both the holotype and paratypes of Eunectes beniensis.These data have been reviewed, corrected, and augmented with new specimens to construct a distributional map for the species.(AMNH 10924) used was originally reported as "Trinidad, Beni, Bolivien" and without geographic coordinates (Dirksen, 2002).In the subsequent paper by Dirksen and Böhme (2005), a redescription of E. beniensis, the locational data of the holotype was listed again and the coordinates given were based on the city of Trinidad ("11°08′N, 66°10′W").However, Dirksen and Böhme (2005)'s coordinates are incorrect.The correct latitude should be in the Southern Hemisphere, and the stated coordinates given are not for Trinidad but rather near the city of Riberalta, Beni, Bolivia (ca.The coordinates for three of the four paratypes (CBF-1675, NKR-1735, and NKR-uncatalogued specimen) listed by Dirksen (2002) and Dirksen and Böhme (2005) are also erroneous.Dirksen (2002) reported the coordinates for specimen CBF-1675 as "(15°29′ / 63°41′)" whereas Dirksen and Böhme (2005) gave the coordinates differently "15°29′N, 63°14′W".While "S" and "W" were not indicated by Dirksen (2002), Dirksen and Böhme (2005) incorrectly reported the latitude as north and transposed the minutes longitude from 41 to 14. Additionally, the correct department for CBF-1675 is Santa Cruz not Beni.The coordinates for specimen NKR-1735 listed by Dirksen (2002) as "Trinidad (11°08′ / 66°10′)" and Dirksen and Böhme (2005) as "Trinidad (11°08′ N 66°10′ W), Beni, Bolivia" are also both incorrect.Again, the designations of "S" and "W" were not indicated by Dirksen (2002), and Dirksen and Böhme (2005) incorrectly gave the latitude as North; this location is near Riberalta, Beni, Bolivia, ca.430 km northeast of Trinidad.The coordinates of the uncatalogued NKR specimen were listed as "14°81′ / 65°08′)" by Dirksen ( 2002) and later "(14°81′N 65°08′ W), Beni, Bolivia" by Dirksen and Böhme (2005); neither are correct.Dirksen (2002) did not indicate "S" and "W", while Dirksen and Böhme (2005) incorrectly recorded the latitude as North.The coordinates for minutes latitude in both publications were erroneously given as 81, but minutes cannot exceed 60.We determined the correct  Eunectes beniensis has five distinct, black, longitudinal head stripes; one median dorsal, one pair of dorsolateral, and one pair of lateral stripes in contrast to E. murinus which has a pair of lateral head stripes and a large, dorsal, dark olive-brownish triangle (thickly bordered in black) with apex toward snout.Photographs: CBE, RLP, and LRR.minutes to be 51, based on the location of the road (Ruta Nacional 3) from Trinidad to San Ignacio de Moxos, 9 km (direct) from Río Mamoré to Río Tajamuchi.Because of numerous errors and inconsistency with locality data by Dirksen (2002) and Dirksen and Böhme (2005), we are reporting corrected coordinates in Table 2 for the holotype and paratypes of E. beniensis.These revised coordinates are based, in part, on the following locations: 1) general geographic center of the city of Trinidad, Beni, Bolivia, 2) highway (Ruta Nacional 9) between Ascensión de Guarayos and Trinidad, and 3) highway (Ruta Nacional 3) between Trinidad to San Ignacio de Moxos.

Geographic coordinates of the holotype and paratypes. The location data for the holotype specimen
We were able to locate 11 vouchered museum specimens (Table 3) which are important records for Bolivia and specifically the departments of Beni, Santa Cruz, and Pando.With these specimens it is now possible to provide an updated list of verified, georeferenced occurrence data for this species and enhance knowledge of the species' distribution.In addition, a field observation (we were able to confirm the identification from several photographs) is also included on the map and in the table.These new and corrected data will aid in a better understanding of the occurrence of E. beniensis but also improve the very limited knowledge of this species' ecology and natural history.Additionally, although the conservation status of E. beniensis is currently categorized as Least Concern (IUCN 2022), improved delineations of the true geographic range of E. beniensis will aid in future assessments of its status.
The known occurrences of E. beniensis appear to be limited to the departments of Beni, Santa Cruz, and Pan-  less, based on a specimen from Manoa, department of Pando, in the extreme northeastern corner of Bolivia (at the confluence of Rio Abuna and Rio Madeira) and directly adjacent to the Brazilian state of Rondônia, it is highly probable E. beniensis occurs in parts of Brazil.Additionally, our results indicate that the distribution of E. beniensis is probably concentrated in the tri-border area of the departments of Beni, Santa Cruz, and Cochabamba but also likely occurs throughout northern Beni, the department of Pando, parts of La Paz, as well as farther south than previously documented for the department of Santa Cruz (Fig. 4).Furthermore, we agree with Dirksen and Böhme (2005)  It is probable that these two species occupy similar niches with similar habitat requirements and preferences.Our results suggest that E. beniensis is distributed in areas of landscape mosaics that include inland freshwater wetlands and a mixture of herbaceous, shrub, and forest cover.Interestingly, these mosaics are most prevalent in the department of Beni but are also common, albeit across smaller areas, in other parts of Bolivia and South America; these mosaics appear to be an important landscape-level characteristic.While the geographic range of E. notaeus in Bolivia is restricted to the Paraguay river drainage of the Pantanal in the extreme southeastern region of the country, E. murinus and E. beniensis occurs in Bolivia within several Amazon river sub-basins (Ziesler and Ardizzone 1979;Henderson et al. 1995;Dirksen 2002;Kershaw et al. 2013).
It is likely that E. beniensis is more common and widespread than museum and collection records reflect, probably due to the aforementioned difficulties associated with collecting and preserving this species.However, it is imperative to note that more specimens are needed to fully delimit and understand the distribution of E. beniensis in its entirety across Bolivia and possibly into neighboring countries.Additionally, research efforts and investigation in the region of southeastern Bolivia-a potential contact zone between E. beniensis and E. notaeus-is also vital.This will greatly improve not only knowledge of this poorly studied species but also future conservation and management of E. beniensis populations and habitat.

Figure 1 .
Figure 1.Eunectes beniensis (CIRA-945), adult female, collected in Bolivia, department of Beni.This individual had a snout-vent length of 174.2 cm and a tail length of 33.0 cm.Photograph: CBE, RLP, and LRR.
430 km northeast of Trinidad).Interestingly, Wallach et al. (2014) cited this mistake and remarked that the type locality was erroneous; they gave a "correction" ["Trinidad, Beni Dept., NE Bolivia, (14°50′N, 64°54′W)"].While Wallach et al. (2014) corrected the latitude and longitude for the city of Trinidad, they failed to correct the North-latitude error.

Figure 2 .
Figure 2. Drawing of lateral aspect of head of (A) Eunectes beniensis, female (CIRA-945) and (B) E. murinus, male (CIRA-534) showing subocular scales (dark gray) and supralabial scales (light gray).Subocular scales in E. beniensis are in contact with supralabials in contrast to E. murinus which has an additional row of scales between the suboculars and supralabials.Illustration: AVC.

Figure 3 .
Figure 3. Photograph of head (dorsal view) of (A) Eunectes beniensis, female (CIRA-945) and (B) E. murinus, male (CIRA-534).Eunectes beniensis has five distinct, black, longitudinal head stripes; one median dorsal, one pair of dorsolateral, and one pair of lateral stripes in contrast to E. murinus which has a pair of lateral head stripes and a large, dorsal, dark olive-brownish triangle (thickly bordered in black) with apex toward snout.Photographs: CBE, RLP, and LRR.

Table 1 .
Scale counts and meristic data for specimens of Eunectes beniensis deposited in the herpetology collection of the Centro de Investigación de Recursos Acuáticos in Trinidad, Beni, Bolivia (CIRA).

Table 3 .
Sabaj (2020)her specimens of Eunectes beniensis collected from Bolivia based on published literature and museum data (including new records) as well as an additional field observation.Coordinates for UMMZ-56863, CIRA-852, and CIRA-966 are based on textual descriptions for the collection location and coordinates were based on the approx.center of the locations with the centroid coordinates 0.5 km in relation to the perimeter.Coordinates for holotype and paratype specimens incorporate corrected locality data (see Discussion).Abbreviation/coding for Museo de Historia Natural "Noel Kempff Mercado (MNK) followsSabaj (2020).All updated geographic location data listed in decimal degrees.
Reynolds et al. (2018)ains and Amazonian regioUetz et al. 2022).4).Compared to other Eunectes species that occur in Bolivia and surrounding countries (i.e.E.murinus and E. notaeus), E. beniensis appears to have a less extensive distribution(Wallach et al. 2014; Reyn-  olds et al. 2018;Uetz et al. 2022).Muñoz et al. (2016)andReynolds et al. (2018)commented that E. beniensis may also occur in nearby areas of Brazil; however, as to our knowledge, no voucher specimens have been collected outside the borders of Bolivia.Neverthe- in that E. beniensis is parapatric or sympatric with E. murinus in Bolivia.For example, De la Quintana et al. (2018) documented a female E. murinus at the same study site as several E. beniensis in southeastern Beni.Also, Dirksen (2002) noted several E. murinus in extreme eastern Beni along the border with Brazil.