Photo/IllutrationThe Yukuru tablets are set in cases with posts in Tokyo’s Edogawa Ward to allow deer to easily lick them. (Makoto Kogure)

Why do deer loiter around railway tracks?

That question puzzled Norihiko Kajimura, who serves as head of a development and planning team in the building material technology research section of Tokyo-based Nippon Steel & Sumikin Metal Products Co.

In late 2010, Kajimura read a newspaper article about railway operators struggling to reduce the increasing number of train collisions with deer.

Based on the article and other reports, Kajimura became aware that a growing population of deer has resulted in not only train accidents but crop damage and other issues, dealing a heavy blow to agriculture and forestry.

At the time, he was working to start a new business for the company.

“I did not know whether exploring the deer issue would lead to the development of a new business, but I became interested in the deep-rooted problem in modern society,” he said. “No one had succeeded in solving the issue, so I wanted to be the first to overcome the challenge.”

As a first step, Kajimura began studying why the animals intrude onto railways. Even when the deer population rises, they are in no danger of getting struck by trains unless they cross the tracks.

He contacted more than 10 university professors but could not find out why.

So, Kajimura set up 15 automatic infrared cameras around railroads in mountains in Gifu Prefecture in spring 2012 to record when and from where deer come into contact with rail lines. He also examined how long they remained there.

Kajimura found through studying 2,000 to 3,000 videos filmed over a month an unknown fact about a deer’s behavioral pattern: The animals eat grass nearby for 10 minutes or so before entering the tracks, stayed on the rails for around 10 minutes and then returned.

The only items near the tracks are iron rails and concrete sleepers, and no apparent food for deer.

Based on the finding, Kajimura formed a new hypothesis that even experts or railway companies have never come up with, that deer “enter the tracks because they want to lick the rails to ingest iron.”

To test his hypothesis, Kajimura scattered powdered iron over the ground and discovered that deer dug into the soil to consume the powder. When a deer licking the rails was captured on a video, he became convinced that his theory was correct.

“I thought that providing iron for deer in front of tracks will eliminate their reason to enter railroads, leading to a reduced number of collisions,” Kajimura said.

In autumn 2015, Nippon Steel & Sumikin Metal Products started selling a block consisting of iron and salt under the brand name of Yukuru.

Measuring 16 centimeters long, 16 cm wide and 10 cm thick and weighing 5 kilograms, Yukuru is the world’s first attractant exclusively designed for deer.

The word Yukuru comprises the Ainu word “yuku” (deer) and the Japanese word “kuru” (come). The product won the Good Design Award in fiscal 2016 for its excellent ability to attract deer and its attractive appearance.

Yukuru is priced at 20,000 yen ($177), excluding tax, per four pieces and can maintain its shape for six months even when exposed to rain and wind.

When Yukuru was tested along the JR Sanyo Line in a mountain in Okayama Prefecture on one day, a group of six deer appeared soon after 8 p.m., taking turns licking the large caramel-like object on the ground for seven hours before walking off.

Yukuru quickly generated a huge response from not only rail operators but also municipalities and local forest offices that are struggling to deal with deer that damage agricultural fields and forests.

Nippon Steel & Sumikin Metal Products was flooded with requests to use Yukuru to lure deer toward places where traps are set.

Kajimura, 50, continues to monitor where deer wander through the 40 cameras he's placed across Japan. The length of the recorded videos totals 1,125 hours.

Kajimura, who hails from Hirakata, Osaka Prefecture, studied urban planning at Oita University’s graduate school. After entering the predecessor of Nippon Steel & Sumikin Metal Products in 1994, he became engaged in guardrail design.

Because his unique ideas were highly recognized, Kajimura joined the company's development and planning team in 2009. Kajimura said he loves creating things because he devoted himself to carving statues in the art club during his high school days.

Called by his colleagues as “the company’s most free-thinking employee,” Kajimura said his next goal is solving issues relating to torrential rain, since he believes the problem is also “a difficult challenge unique to modern society.”

He and his subordinates are visiting more than 80 municipalities to "chat" with officials in charge of road management and countermeasures against flooding. That is because Kajimura thinks that it is important to build relationships with officials so he can understand what they really think and what is the core of the problem.

“Deer and countermeasures against torrential rain are the same in that making thorough efforts with patience is important for both issues,” Kajimura said.