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‘Landscape of fear’: what a mass of rotting reindeer carcasses taught scientists

أرض الخوف: ما الذي تعلمه العلماء من كومة جيف غزلان الرنة المتعفنة

In August 2016, a park ranger stumbled upon 323 dead wild tundra reindeer in Norway’s remote Hardangervidda plateau. They had been killed in a freak lightning event. But instead of removing the carcasses, the park decided to leave them where they were, allowing nature to take its course – and scientists to study this island of decomposition and how it might change the arctic tundra ecosystem.

Over the years scientists observed the bloated, fly-infested bodies turn into dry skeletons. The latest paper, published by the Royal Society in June, looked at the creation of a “landscape of fear”, as top predators such as wolverines, golden eagles and arctic foxes took advantage of the carrion.

“The landscape of fear framework has provided a better understanding of animal decisions in relation to food and safety trade-offs, predator–prey relationships and how communities are structured across trophic levels,” it concluded.

With laws in place in Europe meaning carcasses have to be removed in most instances, most people will never see this kind of death and decay.

“When we were first there it was a little bit solemn,” lead researcher Shane Frank from the University of South-Eastern Norway in Bø says of the Hardangervidda plateau. “It was sad to see that much life snuffed out so quickly.”

Scientists set up camera traps, recorded faeces and observed the wildlife flocking to the carcasses on the plateau, which is 1,220 metres above sea level and a three-hour hike from the nearest town of Liseth in Hardanger. “Over time, as the reindeer decomposed we gained some distance from that ‘death’ feeling. We were also learning so much, in a way giving meaning to it, and it felt like that was an offsetting factor to that solemnity … It’s silly to deny death as part of life,” says Frank.

Scavenger birds such as ravens, crows and eagles visited the highest density of carcasses in 2017 and then were nearly absent in 2018. The reverse was true of rodents (such as root vole, lemming, bank vole and field vole), which were absent from the site in 2017 and then were everywhere in 2018. Scientists believe rodents were too fearful to go to the site while these larger birds were around. Carcasses are interaction hotspots, but not all interactions are positive: “It’s kind of like, here’s a buffet, you’ve got a lot of hungry folks coming in to eat, and maybe they don’t like one another very much,” says Frank.

Another discovery was that non-scavenger birds such as the meadow pipit, northern wheatear, common reed bunting, bluethroat and lapland bunting all fed on the “bloom” of arthropods, such as blowfly, that developed on the carrion. Meadow pipit were the most common, with up to 80 individuals feeding on the site at once. “The fact that passerines forage on insects at animal carcasses is not a unique phenomenon, but only a few examples exist in literature,” scientists wrote in another paper on the reindeer carcasses published in Ornis Norvegica in December. Further study of how these non-scavenging birds could benefit from carcasses could help conservation efforts.

Rotting bodies also change flora. Surrounding the 323 reindeer carcasses were seeds of crowberry – a keystone species of alpine tundra – that scavengers were dropping around the site. Out of 24 faecal samples from crows, 21 contained viable crowberry seeds, according to a study published in Biology Letters in 2018, that suggests seed banks are likely to build up around carcasses.

It is now widely accepted that leaving dead wood in forests benefits many species, but leaving carcasses is still taboo. This, along with concerns about the spread of disease, means there has historically been little research on how carrion returns nutrients to ecosystems. Frank says: “We’ve been focusing on animals when they’re alive, where they go, and where are they moving. I don’t know if it’s something about mortality, culturally, from the western perspective, that we’re a little bit averse to. I think people are now kind of warming up to cold bodies, at least in wildlife research. Everything is connected, and circular.”

With the escalating climate crisis and increased frequency of extreme weather, mass mortality events, such as the deaths of the reindeer in Hardangervidda, will probably become more common. The Australian bushfires, for example, are estimated to have killed more than 800m animals (excluding frogs, insects and other invertebrates), which will cause long-term changes in ecosystems. Unseasonably warm weather in Kazakhstan in 2015 caused a normally harmless pathogen to wipe out 200,000 saiga antelope in a few weeks, and 1m seabirds starved to death in 2015-16 because of a giant “blob” of hot ocean around north America.

Two decades ago, our understanding of the importance of scavenging was more limited. Now, experts from different disciplines are identifying research opportunities linked to the study of death in the landscape, says zoologist Marcos Moleón from the University of Granada in Spain. He believes we are in “the golden age of scavenging research”, with increasing recognition of the key functions scavengers play in terrestrial and aquatic environments. Looking at scavenged prey means we understand connections and interactions in food webs better, and how they create stable ecosystems. “Especially important are those scavengers that may perform long-distance movements and distribute nutrients over large spatial scales, such as vultures and large mammalian predators,” he says.

This doesn’t translate into policy – carcasses are left to rot in Europe only in exceptional circumstances, such as when they provide food for rare scavengers such as vultures. Large mammals that graze nature reserves are generally considered domestic, so their bodies are removed once they have died.

One famous exception is herbivores introduced to the controversial Oostvaardersplassen nature reserve, east of Amsterdam in the Netherlands. The rewilding experiment – known as the Dutch Serengeti – caused outrage after thousands of red deer, Konik horses and Heck cattle starved in the winter, partly because of the absence of predators such as wolves. Carcasses were left outside in public view, with many protesters condemning the project as “animal abuse”.

Research published in the science journal Plos One in January suggests the red deer carcasses benefited biodiversity in Oostvaardersplassen. After near-complete decomposition, plant biomass surrounding them was five times greater than usual, leading to an increase in plant-eating invertebrates and therefore an increase in predators. This bloom of life lasted for months and spread through food chains – even creating scrubby areas and heterogeneity in the landscape, scientists found.

Source: theguardian

الدوحة – الوطن:

قرر علماء ترك جثث حيوانات فقدت حياتها صعقًا بالبرق بدون إزالتها أو دفنها. فما الذي تم التوصل له بعد سنوات من الملاحظة والدراسة للمنطقة التي شهدت حادث الصعق الرهيب؟

بعد حوالي أربع سنوات من الملاحظة والدراسة، ظهرت نتائج الدراسة التي هدفت للتعرف على الآثار التي يخلفها ترك جثث الحيوانات النافقة دون دفنها أو التخلص منها بأي وسيلة أخرى.

فوفقا لدراسة أجرتها جامعة South-Eastern Norway وتم نشرها مؤخرا على موقع Royal Society العلمي، تسبب حادث مناخي في خلق ما تم وصفه في الدراسة بـ «أرض الخوف»، حيث تقوم الحيوانات آكلة اللحوم كالذئاب والثعالب والنسور بتناول لحوم الحيوانات النافقة.

ففي شهر أغسطس عام 2016، نفق 323 من حيوانات الرَنّة صعقا بالبرق أعلى هضبة هاردنجيرفيدا بالنرويج. وبدلاً من إزالة الحيوانات النافقة، تقرر حينها تركها كما هي دون أي تدخل بشري للسماح لها بالتحلل بشكل طبيعي لدراسة أثر ذلك على النظام البيئي، وفقا لموقع الغارديان البريطاني.

وسمحت التجربة للعلماء بتحقيق «فهم أفضل لقرارات الحيوانات آكلة اللحوم بشأن الطعام، ومقايضة السلامة مقابل الحصول على الطعام، والعلاقة بين المفترس وفريسته، وكيف تتشكل المجتمعات على أساس وفرة الغذاء».

وتوصل العلماء لنتائجهم عبر تثبيت كاميرات لتسجيل حركة الحيوانات المفترسة حول الجثث الممدة أعلى الهضبة الموجودة على ارتفاع 1220 مترا فوق سطح البحر والواقعة على بعد ثلاث ساعات سيرا من أقرب مدينة لها.

ولكن الحيوانات النافقة لم توفر الغذاء للحيوانات اللاحمة فقط، حيث وجدت الطيور طعامًا لها في الحشرات التي تكوّنت على الجثث الممدة، كما لعبت الجثث دورًا أيضًا في توفير بذور لنمو أنواع من التوت. وامتدت الآثار المختلفة لترك الأجسام النافقة دون دفنها للسنوات التالية، إذ ظهرت بالمكان خلال عام 2017 طيور كالغربان والنسور أصبحت شبه غائبة لاحقا خلال عام 2018، ليحدث العكس مع القوارض التي اختفت عام 2017 ثم ظهرت في العام التالي.

ويشير المشرف علي البحث، شان فرانك، إلى أن فكرة ترك الأجسام النافقة لا تزال «تابو» خوفا من انتشار الأمراض، وهو ما يعني محدودية الأبحاث التي تمت عن كيفية تزويد الأجسام النافقة النظام البيئي بالتغذية.

ويرى فرانك أن معظم التركيز ينصب علي الحيوانات وهي على قيد الحياة قائلا: «أعتقد أن الناس اليوم بدأوا يستعدون للتعامل مع الأجسام النافقة، على الأقل فيما يتعلق بأبحاث الحياة البرية».

المصدر: al-watan

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