Jamaican Caving Notes

Dromilly Cave
Monitoring
July 19, 2008
Prepared by R.S. Stewart – Jamaican Caves Organisation

Dromilly Cave, Trelawny, was visited for monitoring purposes on July 19, 2008, by R.S. Stewart, J. Pauel, and I.C. Conolley of the Jamaican Caves Organisation (JCO). The cave consists of two large, separated sections, joined at the entrance chamber: In the eastern section, there are wide breakdown chambers with smaller labyrinthine chambers on the south side. It contains a bat-roost, formerly large, now reduced, with associated fauna, which has been a field site for studies by Dr S. Peck (1975), and Stringer I.A. & Meyer-Rochow V.B (1996). In the western section is a long, narrow chamber that has few bats and associated fauna. Both sections were entered by the JCO team on the afternoon of July 19. Care was taken to minimize disturbance to existing fauna. Observations were recorded and have been compared to records for visits by R.S. Stewart, S. Koenig, and G.O.Graening on February 18 and June 13, 2002, and a visit by G. Van Rentergem in 1993.

Position:

[Reserved], WGS84,  +/- 5m
[Reserved], JAD2001, +/- 5m
Alt: 135 m, +/- 15m

Results:

Bats:

In 1993, the total bat population in the eastern section of the cave was estimated to be 10,000+. In 2002, the estimated total was 1,000+. In July 2008, the estimated total was under 500. The section supplies enough roosting space (bell-holes, etc) for a population in the 10,000+ range.

Invertebrates:

The predaceous fly larvae, Neoditomyia farri (Fig. 1), studied by Stringer & Meyer-Rochow in 1996, were present in 2002 and continue to be in 2008, although the extent is reduced. Prey-catching threads were present only in small, limited areas of the available shelving that serves as anchors, compared to larger areas observed in 2002.

The cave cricket, Uvaroviella cavicola (Fig. 2), continues to be present, with many hundreds seen. We can make no real estimate as to whether numbers have varied since 2002.

The amblypygid, Phrynus (Fig. 3), continues to be present, with several seen during a brief search. The main prey species is U. cavicola. It is expected that the total population of amblypygids will be directly related to the number of crickets, but we can make no estimate on variation in numbers since 2002.

The troglophilic spider, Gaucelmus cavernicola (Fig. 4), continues to be present, although not seen as commonly as in Jamaican bat-roosts with large deposits of bat guano, such as Windsor Cave, Rota Cave, and Marta Tick Cave. Our records from 2002 do not allow for an estimate of variation in numbers.

A beetle was noted, and photographed (Fig. 5), that we could not identify, unrecorded in 2002, and not observed by us in other caves previously. We will attempt to identify the species.

The invasive roach, Periplaneta americana, was not seen in the cave during the visit.

Amphibians:

The frog, Eleutherodactylus cundalli (Fig. 6), is found near the entrance chamber, and at the end of the western section where the passage comes close to the surface (there is a slight airflow here and, evidently, large enough fissures and voids to allow the frog to travel in and out of the cave). Total numbers were similar to 2002, with a density comparable to similar caves that have suitable foraging in the immediate external area.

Speleothems: The cave is well-decorated with stalactites, stalagmites, and helictites.

In 2002, no intentionally broken formations were noted.

In July 2008, two recently broken stalagmites were observed near the end of the western section, evidenced by clean surfaces at the break point (fresh calcite with no patina or mud). Both were originally ~100cm in height, are ~6cm in diameter at the break point, and are separated by ~25cm.

Trash:

Fresh trash was noted, and photographed, immediately external to the cave and in the entrance chamber. It consisted of commercial bottled water (empty – four inside, two outside) (Fig. 7), and a plastic junk-food package (Fig. 8).

Discussion:

Reduction in bat numbers:

It was believed in 2002 that total bat numbers were less than what the roost could support because of guano mining, which had occurred often in the years before (evidenced by fertilizer bags, scoops, and bottle torches, plus local accounts). Mining, even on a small scale, can be very detrimental to the fauna of the cave. In 2008, we did not see signs of a great amount of recent activity, although there may be ongoing occasional visits that we would not see evidence for. However, six bamboo torches (Fig. 9), used relatively recently (the bamboo had not begun to biodegrade), were found in the entrance area and in the start of the eastern section. It is our experience that bottle torches are the preferred lighting used in small-scale guano mining, with bamboo torches used only by local tour guides (e.g. Windsor Cave). It is our understanding that commercial tours to Dromilly Cave have taken place in the last months; it is possible that the torches found were used to light the roosting area for tourism purposes.

The combustion by-products of kerosene torches rise to the ceiling, where the bats roost. In the eastern section of Dromilly cave, there is no airflow other than slight mixing at the entrance. Combustion by-products can be expected to linger for some time before they are flushed out. Repeated burning of kerosene in the cave will have a negative effect on roosting bats and may be part of the explanation for the reduction in numbers noted above.

Reduction in numbers of Neoditomyia farri:

The prey-catching threads of N. farri are very fragile, and can be tangled, and rendered ineffective, by as little as exhaling in their direction from 50cm away. This causes the larvae to expend unnecessary energy rebuilding the threads, while also preventing the larvae from feeding during the process. Increased visitation may be a factor in the reduction in numbers. Another factor may be fewer prey species that are dependent on guano nutrient input as the base of their food-chain. With fewer bats present, as noted above, there is less guano entering the cave.

Reduced numbers of Gaucelmus cavernicola:

The population density of the spider is not as high as what the cave could support if guano deposits remained undisturbed. There are no long-term, deep deposits of fresh fluffy bat guano in the roosting area, and soil compaction is great. Flying prey species, such as fungal gnats, are at low levels compared to sites with deep deposits of guano (e.g. Charles Town Cave, Portland; Marta Tick Cave, Trelawny).

Increase in Trash:

We must note that we have never known a local guano miner at Dromilly, or anywhere else in Jamaica, to buy bottled water. The bottles usually left in caves by guano miners are glass, used as bottle torches. Also, commercial snacks in plastic packages are not commonly seen in caves that are being mined on a small scale. The more likely trash to be found is sugar cane sections, if the mining has taken place recently. There is a strong possibility that the trash observed at Dromilly was the result of tourism.

Speleothem Damage:

The area of the cave where the recently broken stalagmites were found has no guano deposits, and there any none close by in the rest of the western section. Both formations were sheared off at the same angle, indicating it was done in the same period by a stationary person. It is unlikely that a local guano miner was responsible. It is more likely that the damage was caused during a tourist visit.

Conclusions:

Dromilly Cave is on the shortlist of caves the JCO regards as biologically important and highly vulnerable to external threats. In the case of Dromilly, the threats are land-use changes, guano mining, and tourism.

Land-use is not a factor in 2008. It has been consistent since 2002 and we know of no plans that will alter it in the future.

Mining for bat guano may become a greater threat as fertilizer prices rise, but at this point Dromilly Cave has no substantial deposits left. Anyone who sells sediment dug up from the floor will not have repeat customers, and anyone who uses it for their own purposes will probably not bother a second time. But, guano mining has negatively affected the cave in the past, and even casual, unsuccessful attempts to extract guano in the future might do so again.

The most immediate threat is tourism. It is taking place now, and we believe we are seeing adverse effects as a result. The bat numbers are down, and degradation of the site is increasing with regard to trash and speleothem damage. We must note that it is unfortunate that the advice forwarded by the JCO to the parties involved before they began their venture was unheeded. Damage to an important cave might have otherwise been prevented.

Recommendations:

No further tourist activities should take place at Dromilly Cave until an Environmental Impact Assessment has been carried out, and approval from NEPA has been granted.

Mining for bat guano should be discouraged in the local community, with education as the tool in doing so. It is the hope of the JCO that legislation will eventually come into place that prevents mining in important caves, but we believe that education will always be a critical component. We would be happy to take on that task, pro bono, at Dromilly, if NEPA deems it helpful.

Figure 1




Figure 2




Figure 3




Figure 4




Figure 5




Figure 6




Figure 7

>


Figure 8




Figure 9