For the easiest wildlife watching opportunity inside National Key Deer Refuge, head for the trail and observation deck at Blue Hole.
It is a cenote-like pond that is the largest body of fresh water in the Florida Keys.
Location: Big Pine Key
Length: 0.3 mile
Lat-Lon: 24.7060, -81.3800
Bug Factor: moderate to annoying
Open daily from a half hour before sunrise to a half hour after sunset. Bicycles are not permitted on the trail, and pets are not advised so as not to scare away wildlife. Please stay within the marked path to avoid brushing into any poisonwood, which is found all over Big Pine Key and is right along this trail.
From US 1, follow Key Deer Boulevard past the shopping center where the refuge visitor center is located. Pay attention to the speed limit as they are slow for a reason: you may see Key deer cross the road along this stretch, especially at dusk and dawn. A bike path parallels the road the length of the refuge, so you can also park at the visitor center and bike up to the trails. Be sure to lock your bike if you go for a hike. The parking area is on the left, 3 miles past the visitor center.
On tropical islands with karst landscapes, a blue hole is a type of sinkhole where a lens of fresh water (supplied by rain during the wet season) floats atop a layer of salt water seeping in from the sea. If you think of Big Pine Key as a giant sponge, the fresh water soaks down 22 feet, with salt water lying below it. Early settlers dug shallow wells to trap this natural resource, but the population has long outstripped the availability of fresh water on Big Pine Key. While Big Pine Key has the proper geology to create a blue hole, this particular Blue Hole is man-made, forming within a quarry where rock was mined for construction of the Overseas Highway. By exposing the fresh water lens in the karst, the Blue Hole is the primary source of fresh water for the wildlife of Big Pine Key.
0.0 > Two trails lead from the trailhead. The one to the right is a short spur to an overlook that gives you a quick glance over Blue Hole.
Return to the trailhead and take the trail to the left, keeping right at the next fork. The trail winds through an area planted with native trees such as pigeon plum, gumbo limbo, and silver buttonwood, and deposits you at an observation platform overlooking Blue Hole.
Look down. The water is clear, and you’ll see a constant parade of aquatic life. Large Florida softshell turtles drift through the shallows. Bluegill, bass, and bream dart between the coontail. Watch for the bobbing heads of Florida cooters and the Florida mud turtle as they scoot across the limestone bottom. A massive giant oscar noses up to the platform piers. If you see an alligator, don’t be surprised. They often hide in the shade that this deck provides.
Leaving the platform, follow the worn path to the right. It makes an arc around Blue Hole. It’s in this area that we’ve most commonly seen Key deer grazing. This is one of the rare places in the Lower Keys where the deer have access to copious amounts of fresh water, no matter how dry the adjacent pine rocklands may get.
0.1 > When you get to the Y junction and see a paved road on the left, keep to the right. There are several open spots with clear views across the pond. The trail soon ends at an “Area Closed” sign with a fence, blocking off the rest of the quarry road to enable deer to access Blue Hole without human disturbance.
0.2 > Return back the way you came, but take the natural path to the right. This loops through the native plant garden and arboretum, with names of the plants mapped out on the kiosk by the trailhead. The full walk is slightly more than a quarter mile.
Blue Hole is shown in BLUE on the map below.