Today’s marine survey revealed a vibrant and encouraging array of marine life, highlighting signs of ecological resilience following the 2023 floods.

Below is a list of species observed:

🐠 Fish

• ​Lithognathus mormyrus (Striped Seabream)
• Serranus cabrilla (Comber)
• Serranus scriba (Painted Comber)
• Coris julis (Mediterranean Rainbow Wrasse)
• Thalassoma pavo (Ornate Wrasse)
• Chromis chromis (Mediterranean Damselfish)
• Diplodus sargus (Sargo)
• Diplodus annularis (Annular Seabream)
• Diplodus vulgaris (Common Two-banded Seabream)
• Sarpa salpa (Salema Porgy)
• Genus Atherina (likely Sand Smelt, species undetermined)
  
  

🪼 Invertebrates​

• Cratena peregrina (Wandering Cratena)
• Thuridilla hopei
• Chondrosia reniformis (Kidney Sponge)
• Family Serpulidae (Serpulid Tubeworms)
• Leucothea multicornis (Comb Jelly)
  

​🪸 Algae, Seagrasses & Cnidarians​

• Cladocora caespitosa (Cushion Coral)
• Asparagopsis taxiformis (Red Sea Plume) 
• Wrangelia penicillata (Pink Bush Alga)
• Acetabularia acetabulum (Mermaid’s Wine Glass)
• Posidonia oceanica (Neptune Grass)

This encouraging biodiversity snapshot underscores the importance of ongoing post-flood monitoring and habitat protection.

In July 2024, during a field visit to the remote and stunning Cave of Thetis at Radakia Beach in South Pelion, We spotted something new—something small, winged, and easy to miss. It was Rhinolophus euryale, the Mediterranean Horseshoe Bat. This was the first time this elusive species had ever been recorded in the cave.

But this wasn’t just a “tick the box” kind of observation. It was part of something much bigger.

Citation of the published article: Taklis Christos. Updated bat (chiroptera) records from the cave of thetis, south pelion, greece. Acta Entomol Zool 2025;6(1):189-191. DOI: 10.33545/27080013.2025.v6.i1c.205​

Why this research matters?

This latest discovery adds a new species to the known bat community of the Cave of Thetis, which had previously only included Miniopterus schreibersii (Schreibers’ Long-fingered Bat), first documented there in 2019. In 2021, Christos Taklis observed juveniles of that species inside the cave, confirming that the site is more than just a temporary roost—it's a breeding ground.

This means the Cave of Thetis isn’t just a cool place to explore—it’s an important home to species that are considered Vulnerable on the IUCN Red List.

And what makes this even more significant is that the 2024 survey was conducted as part of the Wildlife Recovery Survey: After the September 2023 Floods in Pelion. We were looking to see what had survived, what habitats were damaged, and how resilient the wildlife of the region really is.

The presence of both species—especially a new one—after such a major environmental disruption is a hopeful sign.

What do the results tell us?

• Long-Term Roosting: Miniopterus schreibersii has used the cave consistently for over five years, even raising young there. That’s long-term commitment in bat years.
  
  
• New Presence of Rhinolophus euryale: The discovery suggests that the cave may support more biodiversity than previously thought—or that species are shifting their roosts in response to environmental pressures.
  
  
• Resilience Post-Disaster: Even after catastrophic flooding in 2023, bats are returning to their roosts (or they never left). That tells us something about the ecological value and stability of this site.
  
  

Why we should care?

Bats might not get the spotlight that dolphins or bears do, but they are absolutely crucial to ecosystems. They eat insects (many of which are pests), pollinate plants, and disperse seeds. A single roosting site like the cave of Thetis can be the lifeline for entire local populations.

When we lose caves like this—or when they're disturbed by noise, tourism, or development—we risk losing more than just a handful of bats. We chip away at a fragile, interconnected ecosystem.

That’s why this research matters. That’s why we need to keep exploring, documenting, and protecting places like the Cave of Thetis.

Curious to see the cave or learn more about the species?
📸 Check out photos and observations on iNaturalist.
🦇 Follow updates from my conservation work at Merman Conservation Expeditions.

The September 2023 floods in Pelion, Greece, were a devastating natural disaster, with significant ecological consequences for both terrestrial and marine ecosystems in the region. Our project, Wildlife Recovery Survey: After the September 2023 Floods in Pelion (Greece), aims to assess the impact of these floods on local biodiversity through comprehensive wildlife surveys in the affected areas.

​During the marine survey conducted on October 6, 2024, the entire sea area of Theotokos Beach showed no signs of marine life, except for scattered dead leaves of Posidonia oceanica. However, a small section measuring approximately 10 meters by 4 meters was an exception. This area contained a submerged Plane tree (Platanus orientalis) and fragments of broken concrete from the boat slip, debris left behind by the September 2023 floods. Only in this zone were any fish and marine species observed, which, based on previous years' surveys, are unusually rare for this location and time of year.

The September 2023 floods in Pelion, Greece, were not just a natural disaster; they were an ecological event with profound implications for the region's terrestrial and marine ecosystems. Among the many species affected by the floods, the Common Stingray (Dasyatis pastinaca) has drawn particular attention, especially the juveniles that we were fortunate to document during the Wildlife Recovery Survey: After the September 2023 Floods in Pelion (Greece).

The Importance of Juvenile Stingrays

​Juvenile stingrays are a critical indicator of the health of marine ecosystems. Their presence suggests successful breeding and a suitable environment for growth and development. In the context of Pelion, the discovery of juvenile Common Stingrays is particularly significant because it indicates that, despite the ecological upheaval caused by the floods, the conditions in the coastal waters still support the early life stages of this species. 

This observation was made today, September 3, 2024, at the beach of Theotokos in South Pelion, Greece.​ Additionally, the nearby beach of Liri holds the distinction of being the first officially recorded and studied nursery area for the Common Stingray (Dasyatis pastinaca) in Greece.

Stingrays, like many marine species, have specific habitat requirements during their juvenile phase. They typically prefer shallow, sheltered areas with abundant food and low predation pressure, often favoring seabeds composed of mixed sediments, including sand and rocks. These areas provide not only sustenance but also refuge, which is vital for their survival.

The Impact of Habitat Changes on Juvenile Stingrays

The floods in Pelion dramatically altered the seafloor composition at Theotokos beach, transforming a significant portion of the seafloor from a rocky to a predominantly sandy substrate. This change can significantly impact juvenile stingrays for several reasons:

1. Loss of Shelter: Rocky substrates offer crevices and hiding spots that juvenile stingrays use to avoid predators. A shift to a sandy bottom reduces these refuges, potentially increasing predation rates on young stingrays.
   
   
2. Altered Food Availability: The composition of benthic (seafloor) communities can change with the substrate. Rocky areas typically host a variety of invertebrates, such as crustaceans and mollusks, which are key prey items for juvenile stingrays. A sandy substrate might not support the same diversity or abundance of these prey species, leading to nutritional stress for the stingrays.
   
   
3. Breeding and Nursery Grounds: The suitability of breeding and nursery grounds is critical for the continuation of stingray populations. If the altered seabed conditions are less conducive to supporting juveniles, it could lead to a decline in local stingray populations over time.

On July 20th, 2024, a team of the project participants embarked on a significant wildlife recovery survey at the picturesque Radakia beach, located in the southeast region of Pelion, Greece. This survey was part of a larger initiative, the Wildlife Recovery Survey: After the September 2023 Floods in Pelion, aiming to assess and document the impact of the catastrophic floods on the local fauna.

Survey Location: Radakia Beach Sea Cave

Radakia beach is renowned for its natural beauty, featuring stunning sea caves that provide a unique habitat for various species, including bats. These caves, carved by the relentless waves of the Aegean Sea, offer a sanctuary for chiropteran species, making them an ideal location for this survey. In Greek Mythology, Radakia is known for the cave of Thetis.

Bats in Focus: Miniopterus schreibersii and Rhinolophus euryale

During the survey, the team recorded two primary species of bats inhabiting the sea cave: Miniopterus schreibersii and Rhinolophus euryale.

Miniopterus schreibersii, commonly known as Schreiber's bat, was found to be the predominant species in the cave. These bats are characterized by their long wings and swift, agile flight, which enable them to navigate the narrow and twisting passages of the cave with ease. They are a key species in the region, contributing to the ecological balance by controlling insect populations.

Alongside Schreiber's bats, Rhinolophus euryale, also known as the Mediterranean horseshoe bat, was observed. This species is distinguishable by its unique horseshoe-shaped noseleaf, which aids in its sophisticated echolocation abilities. Rhinolophus euryale is particularly sensitive to environmental changes, making its presence a critical indicator of the cave's ecological health post-floods.