Complex sentence: Zebra spiders are often noted for their awareness of humans upon noticing someone observing them, they can be seen raising their head, and usually change behavior (hence why "salticus scenius", theathral jumper).
Split into simpler sentences: Zebra spiders are often noted for their awareness of humans. Upon noticing someone observing them, they can be seen raising their head, and usually change behavior (hence why "salticus scenius", theathral jumper).