In his poem, John Clare depicts the mouse as an "odd" and "grotesque" maternal figure. When he disturbs a ball of grass that he imagines is a bird's nest, a mouse bolts out with "all her young ones hanging at her teats."
To Clare, the mouse and her babies present an incongruent picture. When her hiding place is disturbed, the mother mouse flees with her nurslings still hanging onto her. It is clear that Clare is unused to seeing this "odd" picture in nature. Basically, nature takes him by surprise. What the poet could be getting at is that nature is not circumscribed (restricted or confined) by our own expectations or by our preconceived notions.
Clare is literally surprised to have come across the mother mouse and her "young ones." He had been expecting a bird to emerge from the nest. Instead, he sees baby mice clinging to their mother for dear life as she makes her way to safety. Interestingly, Clare was himself a laboring man during his married years. His wife, Martha Turner, was the daughter of a neighboring farmer.
Martha and John Clare had seven children. Throughout his married years, Clare continued to write poetry. However, he had difficulty earning enough to support his large brood. His first book of poems, Poems Descriptive of Rural Life and Scenery, earned him great acclaim. However, his subsequent works netted him little profit. Eventually, the stress of his domestic responsibilities took a toll on him, and he became an alcoholic.
Clare was eventually committed to an asylum, and he spent the last twenty-three years of his life at St. Andrews Asylum in Northampton. It was reported that he wrote the best of his poetry during this period.
Now, how does Clare's background relate to the "odd" and "grotesque" maternal figure that the female mouse represents? Some literary experts believe that Clare equated his own tenuous position with that of the mother mouse. Like the mouse, Clare was weighed down with the burden of providing for his large brood. It is very possible that he felt suffocated by his responsibilities. To Clare, such burdens may have been as "odd" and "grotesque" in nature as they were in the human world.