🕳🐇 Follow the rabbit!

🥰 When I was on Baltrum in May, I also saw some young rabbits. They're so cute! I photographed one (picture 3).

🐰 European Rabbits (Oryctolagus cuniculus) were introduced to the East Frisian Islands early on. On Baltrum, the species has been recorded since around 1700. A regulation from 1869 ordered their extermination, which caused populations on several islands – including Baltrum – to disappear by the end of the 19th century.

🐰 Rabbits were released again only in 1962. Today, at least 2,000 animals live there on average. Some are descendants of escaped domestic rabbits (Oryctolagus cuniculus domesticus), but over time the natural fur color of wild rabbits has prevailed. As on other East Frisian Islands, Baltrum also has animals with different fur colors. Black rabbits are called "pastors".

🐰 Rabbits have a strong influence on the island’s ecology: their digging and burrowing loosen the soil, create open patches, and thus promote a greater variety of animal and plant species. In older dune areas, this can start new succession processes, increasing both landscape and biological diversity.

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🕊🔭🐒 I observed some birds!

🪶 In the partially flooded salt marshes, numerous black-headed gulls (Chroicocephalus ridibundus) gathered to feed. Their cries could be heard for kilometers.

🪶 On a sea buckthorn bush, a male white wagtail (Motacilla alba) in breeding plumage is perched. In non-breeding plumage, adult birds lack the black markings on the head.

🪶 If you got too close to the Eurasian oystercatchers (Haematopus ostralegus), you immediately felt a pang of guilt. Their piping calls have something reproachful in their tone.

🪶 Common pheasants (Phasianus colchicus) can be encountered everywhere. The colorful males are often heard calling, while the hens try to remain inconspicuous with their chicks.

🪶 A barn swallow (Hirundo rustica) is nesting in a shelter. I remember that they nested in exactly the same place back in my childhood.

🥚 A mysterious egg! Which dinosaur laid this?

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🌊✨️ At the beach of Baltrum, the sea washed up the delicate skeleton of Echinocardium cordatum, a heart urchin. Its sharp spines are gone, leaving only the pale, fragile shell with fine patterns.

🫧🤍 The heart urchin lives under the sea, buried in soft sand or mud, up to 15 centimeters deep. It uses its small spines to dig and feeds by filtering tiny food particles like the decomposing remains of organisms and plants (detritus) from the sand around it.

👽🪸 Sea urchins may look very alien at first glance, yet they are actually more closely related to us humans than to snails or insects. This is because sea urchins – just like starfish – belong to the echinoderms.

🪞🤔 If you only look at their appearance, you might think: Wait a minute! Starfish and sea urchins look nothing like most animals. Many animals – including humans – have two mirror-image halves (bilateral symmetry). Echinoderms, however, are radially symmetrical, usually with five identical sections. That might make it seem like they’re even less related to us than snails or insects, which also have two symmetrical sides.

🧬🔬 But appearances can be misleading. Echinoderms, like all vertebrates, belong to the deuterostomes. Snails and insects, on the other hand, are part of the protostomes. A key clue: echinoderms are bilaterally symmetrical in their larval stage. It’s only later in life that they develop their characteristic radial symmetry.

👄♻️ The fundamental difference between protostomes and deuterostomes shows up very early in embryonic development: in deuterostomes, the first body opening (the blastopore) becomes the anus, and the mouth forms later. In protostomes, it’s the other way around – the blastopore develops into the mouth.

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🪸 In my hand, I’m holding a piece of bladderwrack (Fucus vesiculosus), a seaweed commonly found along the Wadden Sea coast. The small, round bladders are not fruits but flotation organs. They help the seaweed stand upright in the water so its flat fronds can catch as much sunlight as possible. This is essential for photosynthesis – the process of turning light energy into nutrients.

🌊🫧 The bladders are filled with a mixture of gases. This is mainly oxygen, which the seaweed produces during photosynthesis, and nitrogen, which diffuses in from the surrounding seawater. Carbon dioxide, which the seaweed needs to grow, is almost absent because it is used up immediately. Thanks to this high oxygen content, the bladders provide enough buoyancy to keep the seaweed floating, allowing it to capture as much light as possible even at high tide or in murky waters.

🧫🔬 From a biological point of view, Fucus vesiculosus is a brown alga. It belongs to a group called the Fucales within the family Fucaceae. Even though it looks like a plant and makes its own food through photosynthesis, it is classified in a broader group called Stramenopiles, which also includes diatoms (tiny plankton) and some organisms that don’t photosynthesise at all. How exactly brown algae fit into the tree of life is still being studied, and researchers continue to discuss their relationship to other algae and to the ancestors of land plants.

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Fungi, algae and moss 🍄‍🟫🦠✨️

⛰️ Moss and lichen carpet in the Baltrum grey dunes

🔍 Cladonia portentosa is a shrub-like lichen whose main body consists of fungal tissue. It is one of Germany’s specially protected reindeer lichens. Lichens are always in a symbiotic relationship with algae or cyanobacteria. In a thin layer within the thallus – the body of a lichen – tiny green algae (mostly Trebouxia species) carry out photosynthesis, supplying the fungus with nutrients. In return, the fungus protects the algae from drying out and provides them with a habitat – a partnership that enables survival in the dry, nutrient-poor dunes.

🌍 Here, the lichens often grow alongside heath star moss (Campylopus introflexus). This moss is not native to Baltrum but originates from the Southern Hemisphere (southern South America, South Africa, southern Australia, New Zealand). Since 1975, however, it has spread widely and is now the dominant moss species on the island. Together, moss and lichens form a resilient ground cover that anchors the dune sand and, in many places, shapes the characteristic appearance of the island’s grey dunes.

🍄‍🟫 A single mushroom

🏐 In the last picture, I show a mosaic puffball (Handkea utriformis, also known as Lycoperdon utriforme, Lycoperdon caelatum, or Calvatia utriformis). This species is common across the northern temperate zones and is typically found growing alone or in small clusters. It prefers sandy, open grasslands or heathlands and is often encountered in coastal areas. The fruiting bodies usually appear from summer into late autumn.

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🤔 What do you think I’m holding in my hand?

🔍 If you’re thinking of a seaweed, you’re already halfway there! But apart from its branching structure, there’s not much of the seaweed left to see. That’s because it has been colonized and completely covered by a colony of tiny animals! These are moss animals (bryozoans), more specifically Electra pilosa.

🏘🦠 Moss animals usually form colonies (zoaria) made up of many individual animals (zooids). Each zooid consists of a soft body and a protective shell.

🪸🤝🪸 Within colonies, there is a division of labor. Strongly reduced individuals form stalk segments, tendrils, or root-like filaments. Other zooids produce reproductive cells – still others become "nurse" zooids or develop into bird’s-head-shaped avicularia or vibracularia, which prevent other organisms from settling on the colony. In these specialized zooids, both the tentacle crown and usually the gut are reduced.

🏡🦠 In short: the seaweed is mainly just living space for Electra pilosa, not a partner. For the seaweed itself, it is usually more of a burden than a benefit.

⛴️🪸 Moss animals can cause damage or maintenance costs to ships, harbor structures, and water management facilities through heavy growth.

💉🧫 On the other hand, they produce chemical compounds that are the subject of medical research, including the potential anti-cancer agent bryostatin 1.

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