Natural wildlife-drinkable water availability update 4/11/2018
Save Our Key Deer continues to monitor salinity levels at natural freshwater sources within Key deer habitat, and collected the latest data 4/10-11/2018 for Big Pine and No Name Keys. Southern Florida is experiencing one of the worst dry seasons on record (since the eighteen hundreds), with numerous mainland regions having officially been declared being under “severe drought conditions” by the National Weather Service. It is thus no surprise that the number of natural wildlife-palatable water sources in the Keys has rapidly diminished as well, and is creating a stressful situation for many species. SOKD’s latest results:
Big Pine Key: SOKD sampled 19 sites throughout the main island, including sites last sampled in late January. Only 2 sites have water salinities below 15ppt: 1) the “Blue Hole” 12.7-12.9ppt and 2) a large (and deep) artificial pond on private land south of Watson Blvd. Solution holes that had readings below 5ppt at the end of January are now in the 15.4 – 24.4 ppt range. All other sites sampled are either dried up or have salinities above 18ppt, some actually being hypersaline relative to sea water, as they evaporate and concentrate their salt content. We assume there are likely other sites with relatively low salinities, but our sampling results are indicative of their sparsity. SOKD also resampled 6 sites in the vicinity of Long Beach Drive, where no natural wildlife-potable water was found already in January. The situation continues, with many of the sites now having salinity twice that of seawater, as they continue to evaporate. The water situation there is now as bad or even worse than after Irma’s passage.
No Name Key: SOKD resampled 14 sites that include both open ponds and solution holes. The ponds, concentrated in the central part of the island, have either dried up or contain salinities above 30ppt (vs. 23-25ppt range in late January). 7 sites in the solution hole area show salinities in the 14-19ppt range, with one notable exception: a relatively deep, large site that showed 5.6ppt in early March and is holding at 6.4ppt. Another site showed 12.3ppt. The ample deer hoof-print trails and raccoon prints around both of these sites indicate that NNK wildlife is heavily dependant upon these two “last stand” water sources.
These results underscore SOKD’s earlier contention that this year’s abnormally dry conditions which followed hurricane Irma’s saltwater inundation of most fresh water containments have created a very critical water situation for wildlife. The fact that singular drinkable water sources still exist in one or a few portions of the two islands does not alleviate the situation and does not, as per comments by long-time Keys residents, represent a relatively normal condition for this time of year. Since none of the natural water sources have flowing water, the greatly increased concentration of animals and birds also raises the potential for disease transmission. This situation will not be alleviated simply by a passage of a thunderstorm or two, and NOAA is predicting continued abnormally dry conditions to persist for the next two months. Therefore, SOKD continues to advocate that wildlife-friendly residents provide drinking water on their property, and continues to call upon Refuge management to do so on federal and state lands –
which they so far have not done, nor have they, to our knowledge, conducted any salinity testing on their own in recent months.
One final note regarding the widely quoted 15ppt salinity tolerance cutoff for the Key deer: This value is used by the Refuge and cited as fact in recent scientific publications. It should be noted, however, that it is not based on any controlled experiments. Rather, it is based on two initial observations: 1) a 1974 “Final Report to the US Fish and Wildlife Service” by Klimstra et al. in which he noted visual observations of Key deer drinking out of sources as high as 14ppt during draught conditions; 2) M. Folk (a Klimstra protégé) wrote in his 1991 MS thesis that he observed deer tracks leading to water sources with even higher salinity. More recent publications adopted the 15ppt figure and quote these two sources, but no further direct assessments or experiments were ever done. So it is not known how long Key deer can actually survive drinking water with nearly half seawater concentration, since that is generally not sustainable by other mammals.
Dr. Jan Svejkovsky, SOKD treasurer
The photos below show a few of the water testing areas from today and yesterday and some recent, concerning photos of emaciated, mangy, malnourished, sick-looking Key deer posted by residents on our Save Our Key Deer facebook page: