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I found such a claim in an article here: http://nowiknow.com/the-thin-red-deer-line/

But that was a long time ago, especially if you’re a deer — they only live about ten or so years in the wild. There are few, if any, who are old enough to have lived through the Cold War. Most of the fences are gone, too, so there’s really nothing keeping West German and Czech deer from visiting one another.

Yet, the deer won’t cross the line.

The article cites and links to a "The Wall Street Journal" article from 2009 which is not accessible due to paywall.

The site http://nowiknow.com doesn't look like a reliable one. Looking at the headings it seems more like a "shocking facts" website.

Q: Is the claim true? Is there really some "invisible border" passed between generations of deer? Or maybe deer just don't migrate that much for it to be really an issue?

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Przemysław Czechowski
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    That study is from 2015, the WSJ article is from 2009. It is not the study referred to. – Jack Aidley Apr 12 '19 at 15:03
  • I can find reports of the story from more credible sources - e.g. https://www.bbc.com/news/world-europe-27129727 - and the name of the principle researcher behind the study - Pavel Šustr - but I can't locate the actual research reporting the divide. Perhaps this will help someone else find it? – Jack Aidley Apr 12 '19 at 15:08
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    @JackAidley thx, edited – Przemysław Czechowski Apr 12 '19 at 15:09
  • @JackAidley I found this: https://bioone.org/journals/Wildlife-Biology/volume-15/issue-4/08-014/New-Possibilities-of-Observing-Animal-Behaviour-from-a-Distance-Using/10.2981/08-014.full - seems like the right one – Przemysław Czechowski Apr 12 '19 at 15:13
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    [Sheep can be hefted](http://sciencesearch.defra.gov.uk/Default.aspx?Module=More&Location=None&ProjectID=15631), i.e. trained to graze a particular area and to pass this training on to many later generations, so it would not be a surprise if other mammals can be too. – Henry Apr 13 '19 at 00:01
  • @PrzemysławCzechowski why didn't you make an answer (not just a comment) that you found the original study and solved your question? – Maxim Apr 15 '19 at 09:19
  • @PrzemysławCzechowski While the article is interesting, I don't think it answers the question. The article you cited is about tracking Red Deer using different methods and not specifically about differences in behavior relative to an invisible line. Also note that the paper was published in 1 December 2009. The WSJ article is from 1 November 2009. – Barry Harrison Apr 16 '19 at 08:04
  • A quick look on a topographic map (http://en-gb.topographic-map.com/places/Czech-Republic-139583/) shows that the border between Czech Republic and Germany seems rather hilly high altitude terrain. Maybe this is just the natural cause why deer don't traverse? – Scrontch Apr 16 '19 at 09:16
  • @Scrontch I just thought about the same. Political borders tend to follow natural barriers (rivers, lakes, mountain ranges or generally unhospitable areas). I wouldn't find it unlikely, that it even without any man-made barriers along the border, simply is inconvenient for the deer to cross. In the area north of Grafenau, which is especially mentioned in the linked article, the state border mostly runs along a small river. – Tor-Einar Jarnbjo Apr 17 '19 at 17:15

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The Pacific Standard magazine published a critical look at this claim which is available for free on the web. It says the original study started in 2005 and may have received some attention while it was still in progress, but wasn't formally published until 2011. I believe it was published in German, but I cannot find a working link to it. It seems to have gotten a lot of attention in the international press around 2014, and the findings were somewhat exaggerated in much of this reporting. It is not that the case that the deer know where the line was and refuse to cross it, just that their learned patterns of migration show the effects of the historical border.

Here are some key quotes from the lead investigator of the original study, Pavel Sustr from 2014:

"It's going to absolutely the same place in the following years," Sustr says. "And because of this traditional behavior, they are still somehow respecting the former Iron [Curtain]."

He notes that some deer are making the leap into uncharted territory, but the winds of change blow slowly in the mountains of Central Europe.

"More animals in the last year are crossing [the border], but the trend, or the change, is quite slow because of the traditional behavior of the deer," Sustr says. "The young deer [during its] first year follows its mother [and] the mother is teaching [it] the area. So, more or less, the behavior of the mother [determines] the area which is used by the deer in later years."

EDIT 4/17/2019: It looks like key German-language study in which this claim originated went through several publications, most recently revised in 2010. If anyone reading this understands German, picking out and translating some key quotes might be helpful.

However, the most interesting source I found in English seems to superscede the evidence from that study:

Joerns Fickel, Oleg A. Bubliy, Anja Stache, Tanja Noventa, Adam Jirsa, Marco Heurich, "Crossing the border? Structure of the red deer (Cervus elaphus) population from the Bavarian–Bohemian forest ecosystem", Mammalian Biology, Volume 77, Issue 3, 2012, Pages 211-220, ISSN 1616-5047, https://doi.org/10.1016/j.mambio.2011.11.005.

This is a genetic study which suggests that the deer are breeding across the former border.

In the years from 1994 to 1997, the genotypic differentiation between red deer populations of the Bavarian–Bohemian forest ecosystem was low, yet significant (FST= 0.0471,p< 0.001; Kuehn et al. 2003). In late 2009, however, that small genetic distance had even diminished and become insignificant (FST= 0.009,p= 0.383), indicating genotypic admixture between the two for-merly separated red deer populations of the Bavarian–Bohemian forest ecosystem. This result was corroborated by the Structure analysis, which suggested a single genotypic cluster. The detected genotypic admixture clearly rejected the hypothesis of a behaviourally triggered secondary enforcement of a previously long-term interrupted (by a State border barrier) gene flow in red deer. In contrast, our results supported the alternative hypothesis of secondary admixture between populations from both sides of the former border, leading to a collapse of the earlier (even if small) genotypic differentiation.

The paragraph goes on to discuss the evidence that males in particular are moving across the former border while females are more inclined to stick with their "traditional" territory.

So overall, there may be a grain of truth to the idea that the border had a lasting effect on deer behavior, but again, popular reports have exaggerated the evidence.

Brian Z
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  • good catch about the ongoing investigation being published ahead of time: i was looking for publications by sustr that would fit, but none came up before 2010. i found a dead link, though, to a page by the bavarian park service, that purported to show the same thing. linking article is from nov. 4 th. so perhaps sustr shared some pre-results with the park service, or cooperated with them, they published a gloss on that, and the media ran with it. https://www.metafilter.com/86388/Worlds-Longest-Invisible-Fence – bukwyrm Apr 17 '19 at 04:48
  • Just expanded this answer with a link to a peer-reviewed study and the original German-language source. – Brian Z Apr 17 '19 at 17:16
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    @BrianZ Actually, I don't see how that German source contributes to the question. I didn't find the iron curtain and former borders mentioned. However, they state on page 10 that the deer population in most German federal countries is restricted to certain areas that are defined by law (mostly for historical reasons). Outside these areas deer have to be hunted, which prevents seasonal movement,, population exchange or establishment of new populations. The following pages are about how to improve the situation for deers. – Arsak Apr 17 '19 at 18:15
  • Thanks @Arsak. Perhaps it was changed significantly since the 2006 version cited by Finkel et al 2012. – Brian Z Apr 17 '19 at 19:11
  • I've deleted my comment. The genetic study is a great find! – Barry Harrison Apr 20 '19 at 20:44