Non‐random distribution of ungulate salt licks relative to distance from North American oceanic margins

Abstract

Aim: Terrestrial deposition of aerosol marine sodium declines with distance from coastlines. Salt deprivation in vertebrate herbivores and salt-seeking behaviours should hence increase with distance inland. We analyse published geospatial data on ungulate-patronized salt licks to test whether they are non-randomly distributed relative to distance from oceans and elevation.Location:Canada, Alaska and the contiguous United States.Taxon:Cetartiodactyla (even-toed ungulates).Methods:We determined the land area and median elevation of 100 km increments from the North American coast. The null model of the expected number of licks within each interval was determined by the ratio of the interval's land area to the total land area, multiplied by the total number of licks. We asked whether the number of licks further from coastlines was significantly higher than chance. We also assessed whether licks occur disproportionately at higher elevations, comparing the median elevation of observed licks to the median elevation within each interval.Results:We found a strong positive relationship between salt lick patronage by ungulates and distance from the coast. Licks occurred significantly less often within, and more often beyond, 500 km inland, and at significantly higher elevations than would be expected by chance.Mainconclusions:These findings indicate that the patronage of salt licks is constrained geographically, and that the foraging behaviour of ungulates and other phytophagous vertebrate taxa may be influenced over large spatial scales by sodium availability. Saltseeking behaviour varies on a wide biogeographical scale across North America, with concomitant implications for vertebrate herbivore behaviour and ecology.

Geophagy by a large herbivore (capybara, Hydrochoerus hydrochaeris) driven by a human sodium supply

“…In our study, consumed soils were artificially fertilized and contained Na concentrations ~2-20× higher than natural mineral licks (Griffiths et al, 2022;Powell et al, 2009) and significantly higher than non-consumed soils and other elements (Table 1). These results are consistent with the reported consumption of naturally Na-rich soils by large herbivores worldwide and the common occurrence of mineral licks in Na-poor regions (Lee et al, 2010;Maro & Dudley, 2022). While herbivores may receive multiple benefits from geophagy (e.g., digestion, additional nutrients), and such benefits may work together to encourage geophagy in many cases, our observations further suggest that Na deficiency acts as a principal driver of geophagy by large herbivores (Duvall et al, 2023).…”

“…Consequently, in Na‐poor regions, plants often contain insufficient Na to meet the physiological requirements of herbivorous animals (Abraham et al., 2023; Duvall et al., 2023). Accordingly, geophagy is generally observed in Na‐deficient ecosystems (Lee et al., 2010; Maro & Dudley, 2022), and nearly all consumed soils contain significantly higher Na concentrations compared to non‐consumed soils (Griffiths et al., 2022; Molina et al., 2014; Powell et al., 2009).…”

Allometry of sodium requirements and mineral lick use among herbivorous mammals

“…This aligns with observations at mineral licks around the world, with females, who often have higher Na demands from pregnancy or lactation, visiting more frequently than males (Calef and Lortie 1975, Montenegro 1998, Atwood and Weeks 2003, Ayotte et al 2008, Kroesen et al 2020, Pan et al 2020, Vasilchenko and Naidenko 2021, He et al 2022) and increasing visitation during reproductive periods (Fraser et al 1982, Pan et al 2020, Vasilchenko and Naidenko 2021, He et al 2022). Furthermore, the occurrence and use of mineral licks appears to be highly associated with low‐Na ecosystems, consistent with our results (Weir 1972, Holdø et al 2002, Lee et al 2010, Dudley et al 2012, González et al 2021, Maro and Dudley 2022).…”

“…Among the most prominently noted adaptations is geophagy (soil consumption) at mineral licks, sites that exhibit elevated concentrations of several nutrients, particularly Na (Weeks 1978, Moe 1993, Holdø et al 2002, Ayotte et al 2006, Powell et al 2009, Lavelle et al 2014, Matsuda et al 2015, Edossa et al 2021, Griffiths et al 2022a). Mineral licks occur in ecosystems around the world, predominately inland regions (Lee et al 2010, González et al 2021, Maro and Dudley 2022), and may provide many additional benefits to herbivores including detoxification of plant defense compounds (Gilardi et al 1999, Brightsmith et al 2008, Reynolds et al 2015), gastrointestinal relief (Krishnamani and Mahaney 2000, Panichev et al 2017, Gomes 2018), and supply of other biologically important minerals such as Ca and Mg (Heimer 1988, Nelson et al 2005, Edossa et al 2021).…”

Monitoring of the habitat usage of Tembadau (Bos javanicus lowi) around salt lick in a forest plantation of Sabah, Malaysia

“…Mineral springs, ground containing salt, or any other mineral is considered a salt lick. It can be found in tropical and temperate regions, especially in South-East Asia (Lazarus et al 2021;Maro and Dudley 2022;Pla-ard et al 2022). Salt lick can provide mineral sources and animal feeding sites (Tawa et al 2022).…”