Spikes in Traffic

We have the dude setup to monitor about 35+ routers going to a VPN concentrator, and for some reason, every 5 minutes we have this spike in traffic on both the core MikroTik that monitors those routers and a much smaller version on each of the 35 other routers.

The way I have the Dude configured is each device (router) only has one service running on it (ping) to just monitor their uptime, and I am also doing an SNMP graph on their IPSec VPN tunnel to the Core router.

So the question is, what is that spike in traffic? Is it the SNMP causing that?

I have attached two images, to show you all what I am talking about.
chart.png
core.png

Those are checkout spikes.. Each tim dude check remote device - this appears.. Not bid deal . have the same