The Lesser Northern Cave System, often overlooked for its sister cave (Greater Northern Cave System) presents the academic community with a resource previously unknown. Ecosystems within caves have been little explored or recorded, especially seemingly small and unimportant ones, which also do not attract the attention of amateur potholers. The Lesser Northern Cave System (which will henceforth been referred to as LNC) was assumed to share many attributes with its sister cave, (Greater Northern Cave System.) Uncommon compounds and co-existence of elements have been discovered within the LNC. This is presumably what has allowed different and, as of writing this, unique cave macro and microorganisms to inhabit the caves. I would urge the scientific community more deeply map and excavate the cave, although it must be noted that there have been several incidents that may incite wariness to do so. Ultimately, the benefits the LNC offer us must not be overlooked.

Initial Discovery and Overview:

Located on Oisin Island, off the coast of Burtonport, Republic of Ireland, the LNC is by no metric particularly notable from the outside, located on a sheer drop into the island’s coastline, wedged between two exposed rocks. The island is almost completely uninhabited, a roughly built house exists for only seasonal researchers and artist types to reside in for six months out of the year. The permanent residents include a few security personnel and scientists employed to monitor areas of particular interest, living in permanent housing near the coast. The discovery of its sister cave, the Greater Northern Cave System, occurred three years previously, in 1973 by Burt Tell during a census of the land birds on the island. The LNC was discovered by a research assistant of Tell’s (who had at this point shifted his attention to the island’s caves). It is predominantly limescale, like others in the region, however has less porous and darker rock features beyond 60m (although this has not been well documented). It is (approximately) 130 m deep and 6.42 mi long. This is larger than its sister cave, however due to its narrow entrance and placement near the shore it was initially assumed smaller. Additionally, within the LNC’s winding cave systems a notable underground river system has formed, which houses and feeds many unique species.

The most known attribute of the LNC is a feature called The Mouth. It was discovered by Zhang Wei, a resident scientific illustrator, during an attempt to record the stone types deep within the cave. Electrical lights had not yet been set up and Wei slipped and subsequently dislodged a large opening that descended into the ground. After going back up to gather more experienced cavers the tunnel was explored. Wei illustrated what he saw below.

The Mouth was described by the other cavers as much less creature like, and simply an interesting formation of the rock. Wei’s portrayal was further discounted as he was known to be an unstable drunk who, after this trip into the cave, became more unhinged until his tragic death only two years later.

Allegations regarding “The Mouth”:

Some speculative stories about The Mouth have formed due to events occurring between 1978 and 1986, before heavy restrictions were enacted to cave access. It is important to note, none of these have been verified and are only recorded within personal accounts. Any attempt to photograph or more formally document the aberrations have been unsuccessful.

1978: A group of potholers visited the caves during a period where there was no resident LNC guide on the island. This was discouraged as the electrical lights and guided pathways had not been completed. As they approached the intersections between The Islands and The Birth Canal (the large opening dislodged by Wei and, having only just been discovered, was the least recorded and lit area of the caving system), 38-year-old Roseland McKay slipped headfirst down into the passage, which, although notable enough to be mapped, was too narrow to travel down without prior positioning. The subsequent events are recounted by Mack Andrews, who travelled with McKay and was the closest to her when she fell into the hole.

“Rose cried suddenly. We couldn’t see and the lights weren’t illuminating where she’d fallen to. Then we heard her bone crack from hitting a ledge, her boyfriend behind me screamed after her and began to run past me. Then we felt a breeze rushing passed us into the cave, like when you breath in for air. Then a low wheeze and when we shone our torches down we could see Roses feet, only a few meters beyond us. What happened after was something of the devil. I was not a religious man prior, but after that day I cling to God to explain what I will describe to you. The walls off the cave began to flex and move, pulling Rose down into the darkness towards the bottom, the wheezing morphed into a low continuous hum and then, all at once her body, whether dead or alive we did not know, was sucked down into a large gaping mouth, which we could only see the lips of from where we stood.”

The above paragraph was published in “Weekly Truth: What Lurks Unseen Among Us” issue.68

Although we know that the group of Roseland McKay, her boyfriend Arthur P. Allan, the author of the paragraph, Mack Andrews and three others did visit the LNC, it is important to note that although Roseland was reported missing, it could not be confirmed to have occurred on the island. Furthermore, her body was never found within the cave system. All parties involved had an avid interest in the paranormal and it can be assumed the story may have been heavily embellished, including the area in which she went missing.

1979: Spurred on by the published report by Mack Andrews, a group of young boys aged between 15 to 17 travelled from Essex to Oisin during the summer vacation. This time resident scientists were available; however, the boys managed to bypass them going into the LNC when night fell. The youngest boy made this statement shortly after being discovered by a junior researcher in the early hours of the morning. The names are withheld to protect the children’s privacy.

Transcription (edited for brevity):

Interviewer 1: “Why did you enter the cave without guides?”

Boy: “[Redacted] had just had his grandfather’s inheritance given to him and we all decided we wanted to see where that girl had gotten eaten up by the cave. We knew there was something going on but it was only rumours and we wanted to be the first to photograph a real-life monster”

Interviewer 1: “Why didn’t you alert anyone of your intentions?”

Boy: “We wanted to be first to record it, [redacted] said you would just like – get in the way. I’m sorry- I’m sorry”

Interviewer 2: “Son, what did you-”

Boy: “Please Jesus take me home, please, I have the money for the ferry in my pocket – oh god” [sobs]

At this time, the boy becomes hysterical, the interview is restarted the next morning.

Interviewer 2: “[Redacted], we didn’t get to ask you about what you saw before you lost your friends yesterday, could we discuss it today?

Boy: “Nothing – just the cave. We didn’t even get that deep, it was darker than we thought it’d be, I got out after an hour.”

Interviewer 2: “So you left the cave without the other boys?”

Boy: “Yes.”

Interviewer 1: “Where did you last see your friends, [redacted]?”

Boy: “A woman came to me, she told me the cave was no longer hungry, and she thanked me, and I left. My friends got too close, and they were eaten.”

Interviewer 1: “Eaten? So, they fell into the cave?” 

The boy nods

Interviewer 2: “Look, I promise you we have our best men under there looking for them right now, but you need to tell us more, where did you see the woman?”

Boy: “In the cave.”

Interviewer 1: “I know you’re shell shocked right now, but you’re not doing any favours by telling us lies, your friends are still out there, alive but scared, and you need to help us. There isn’t no woman, but we know the other boys are in the caves, tell us where you saw them fall.”

Boy: “You won’t find them; you know you won’t find them.”

The interview continues for another 14 minutes, but nothing else of note is stated. The parents of the children would go on to file a lawsuit against Burt Tell, who had acquired ownership of the island. This was dismissed in court due to the lack of any substantial evidence as no bodies were recovered and the only survivor become so incoherent he could not testify in court. Three other missing persons reports have been filed in relation to the cave. These disappearances were of 21-year-old Bruce Allen (1980) and 20-year-old Sam Fenall and Ben Thessiger (1986). After the double disappearance of 1986, the LNC was completely shut off to the public due to pressure to destroy the cave completely. As of writing this, the island is heavily secured by Burt Tell’s personal security.

LNC ecosystem:

A rich and diverse ecosystem inhabits the LNC. The smaller microorganisms range in size from 0.225mm to 0.08mm, with the largest fauna only reaching an average of 10cm. What they lack in size they make up for in range. 2 different species of single celled algae have been discovered within the cave, totalling to 4 species all together. Regarding macroorganisms, two new species of fern have been discovered at the threshold of the cave, the brown bush fern, and the horn fern. Fungi and moss are found deeper in the cave, with examples including (in no particular order): golden shield lichen, silky forklet moss, common tamarisk moss, and jelly ear.

This base of varied vegetation allows a strong network of creatures to exist. Cave spiders make up much of the insect life, being partially supported by a notable population of houseflies that exist throughout the cave. The houseflies are attracted to the caves by Europe’s only exclusively cave dwelling mammals, the short-eared rat and a subspecies of Mustelidae, yet unnamed, referred to as cave ferrets.

Short-eared rats nest near the cave’s threshold, and feed on a mixture of the smaller infant cave ferrets, ferns and occasionally bugs. They have a unique echolocation characteristic; the rat will emit a low continuous shriek which can be used to map out its surroundings. The rat has large eyes that take up half its head, so it is unknown why echolocation is necessary. They have been recorded to grow up to 15 cm in height, and dwarf the cave ferrets in size.


Cave ferrets (also known as blind ferrets) are physically very distinct from other mustelids. They are not classified as ferrets (the name is only colloquial) but they do hold superficial similarities, with long bodies and a carnivorous diet shared throughout the Mustelidae family. These cave ferrets also have a distinct and lingering smell, however noticeably sweeter than other mustelids. They only inhabit the LNC below 50m, forcing the short-eared rat to descend into the cave to eat it’s young. The diet of the cave ferret is made up almost exclusively of the fish inhabiting the underground rivers.

Due to the high concentration of algae in the underground rivers, maintained by the near constant rainfall on the island, large numbers of pink ghost fish have amassed in the LNC. Measuring 10cm in length (near the size of the cave ferret) they navigate the streams with barbels extending from their lips and stomach as they are mostly blind. They have an almost complete lack of pigment, like many recorded cave fish. Due to an outbreak of disease on first contact with the fish, they have been little studied, and the below illustration is one of few in existence.

Folklore regarding the LNC:

The residents of Burtonport have long told stories of a cult like group existing and feeding an aberration on the island. It was told that young women would travel to the island together, seeking freedom from their husbands. They formed a commune and were provided for by the plants and animals. However, occasionally they would need to give human flesh to the ground to continue to live off the land. The folklore reflects an appreciation for the ecosystem on the island, although it is quite fanciful. This instilled a fear within mainlanders to fully embrace the potential of Oisin island as a natural resource.

Similar tales were told by British colonial sailors throughout the 1800’s, these are deemed to be heavily influenced by local tales and the remerging popularity of the “siren” or “female seductress” trope.