import re
 
text = """2013-04-13: BS-440: 10 egg masses observed in vernal pool habitat. Observer noted 3 of the AMJE masses had firm jelly, akin to a 3-wk old AMMA mass, but "bumpier" on outside (membrane and embryo-spacing in the masses were AMJE-like). BS-443: 3 egg masses observed in vernal pool habitat. A few egg masses may have been missed due to poor light conditions. Smith-019: 250 egg masses observed in vernal pool habitat. Observer searched only portions abutting the road (SW margin of pool). Many AMJE masses observed attached to herbaceous vegetation and difficult to differentiate from one another. AMJE egg-mass count is a rough estimate within area searched. 2017-01-01: 23 individuals observed. Egg masses were not present. 2018-07-04: BS-440: All individuals took a break from breeding for the long holiday weekend."""
 
output = re.compile(" (?=\d{4}-\d{2}-\d{2})").split(text)
 
print(output)

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